LUE  PRINT  READING 

or 

Interpreting  Working  Drawings 


E.  M.  WYATT 


UC-NRLF 


75 


V.o* 


BLUE   PRINT   READING 


BLUE   PRINT   READING 


Interpreting  Working  Drawings 


By  E.  M.  WYATT 

Manual  Training   Supervisor 
Houston,    Texas 


THE  BRUCE  PUBLISHING  COMPANY 

MILWAUKEE,    WISCONSIN 


W 


Copyright  1920 
The  Bruce  Publishing  Co. 


PREFACE 


This  book  is  the  result  of  several  years  teaching  of 
blueprint  reading  in  night  schools  and  several  years 
teaching  of  drafting  preceding  it.  The  material  was 
used  for  three  years  in  blueprint  and  mimeographed 
form.  In  this  form  it  was  thoroughly  tried  out.  In 
preparing  it  for  book  form  the  drawings  have  been 
carefully  redrawn  and  the  text  improved  upon  as  ex- 
perience suggested  to  be  desirable.  Essentially  it  is, 
however,  a  tried  text,  one  that  has  been  used  to  teach 
the  reading  of  drawings  to  one  class  of  mixed  trades, 
one  class  of  ship  carpenters,  two  classes  of  house  car- 
penters, and  one  class  of  machinists. 

It  has  been  designed  to  suit  as  wide  a  range  of 
trades  as  possible.  Usually  each  new  principle  is 
illustrated  by  both  a  machine  and  an  architectural 
example. 

In  recognition  of  the  principle  that  we  learn  by 
doing  a  number  of  drawings  are  included  to  give  prac- 
tise in  reading.  At  the  end  of  each  chapter  a  number 
of  questions  are  placed,  a  few  for  the  purpose  of  re- 
view, but  more  to  stimulate  the  study  of  the  drawings. 

The  study  of  mechanical  drawing  has  long  been 
recognized  as  a  sure  method  of  learning  to  read  draw- 


ings. The  Author  knows  it  to  be  effective  but  round 
about,  long  and  tedious.  The  Author  finds  shop 
sketching  just  as  effective  and  much  quicker.  It  is 
essential  that  students  have  some  method  of  expres- 
sion of  the  principles  discussed  in  the  text  and  shop 
sketching  provides  this  admirably. 

When  time  permits  the  book  can  well  be  supple- 
mented with  the  study  of  many  blueprints  supplied  by 
the  teacher  or  the  students  and  much  more  sketching 
than  called  for  herein  can  also  be  effectively  required. 

The  Author  believes  the  book  to  be  well  suited  to 
individual  study  aside  from  its  use  as  a  class  text. 
When  so  used  he  urges  that  the  shop  sketching  be  not 
neglected,  and  that  the  student  seek  criticism  of  his 
drawings  by  some  draftsman. 

Most  of  the  drawings  used  herein  have  been  de- 
signed especially  to  illustrate  the  text.  The  drawings 
"For  8"  Bench  Grinder,"  however,  are  taken  from  the 
excellent  little  books  "First  Year  Lathe  Work"  and 
"How  to  Run  a  Lathe"  published  by  the  South  Bend 
Lathe  Works.  The  Author  gratefully  acknowledges 
the  courteous  privilege  granted  him  to  use  them  in 
this  work. 

THE  AUTHOR. 


TABLE  OF  CONTENTS 

Page 

Preface   3 

I     Introduction    7 

II     Kinds  of  Drawings 9 

III  The  Theory  of  Orthographic  Projection 12 

IV  Meaning  of  Various  Kinds  of  Lines 17 

V     Foreshortened  Lines,  Inclined  Surfaces,  Auxiliary  Projection. .  22 

VI     Scale    Drawing,    Dimensions 27 

VII     Breaks,  Representing  Drawings  as  Broken 35 

VIII     Sections    38 

IX     Bolts,  Screw  Threads,  Machining  or  Finish 43 

X     Rivets— Structural   Steel 46 

XI     Architectural  Conventions 49 

XII     Study  of  a  Set  of  House  Plans 55 

XIII     Study  of  the  Bench  Grinder 71 


INTRODUCTION 


Mechanical  drawing  is  a  universal  language  under- 
stood by  the  artisans  of  all  nations.  The  drawings 
made  by  a  skillful  French  draftsman  are  just  as  read- 
able to  an  American  draftsman  as  those  made  by  his 
fellow  draftsmen  though  he  may  know  no  tongue  but 
his  native  one.  It  is  a  language  with  rules  of  gram- 
mar just  as  any  other  language,  and  a  draftsman  is  a 
good  or  poor  draftsman  very  largely  as  he  observes 
or  violates  these  rules. 

It  is  a  valuable  business  asset  to  many  of  us  to  be 
able  to  understand  and  speak  French,  Spanish  or  some 
other  language  than  our  own.  It  may  be  of  no  value 
to  us  to  be  fluent  writers  or  speakers  in  the  tongue. 
Just  so,  a  great  many  men  in  this  great  industrial  age 
are  finding  it  necessary  to  understand  the  great  uni- 
versal language  of  mechanical  drawing.  It  may  not 
be  necessary  for  them  to  have  a  thoro  by-rule-of- 
grammar  knowledge  but  simply  a  working  knowledge 
that  permits  them  to  understand  a  draftsman  and  per- 
haps on  occasion  to  roughly  "talk-pencil"  themselves. 


Those  who  need  an  expert  knowledge  of  drawing 
must  secure  it  thru  taking  a  thoro  course  in  mechani- 
cal drawing.  For  those  who  by  means  of  reading  wish 
to  acquire  easily  a  working  knowledge  on  this  subject, 
this  course  has  been  prepared. 

The  course  has  been  prepared  with  the  idea  of  giv- 
ing an  understanding  of  the  fundamental  underlying 
principles  of  mechanical  drawing,  a  knowledge  of 
drafting  conventions,  practice  in  the  interpreting  of 
drawings,  and  some  practice  in  expressing  one's  own 
ideas  by  "shop  sketching." 

Mechanical  drawing  is  used  principally  by  two 
great  groups  of  artisans — those  engaged  in  the  build- 
ing trades,  and  those  in  the  machinist  or  allied  trades. 
For  this  reason  the  drawings  in  this  course  are  as 
evenly  as  practicable  divided  between  those  used  in 
these  two  great  industrial  groups. 

The  work  in  "shop  sketching"  is  put  in  to  fill  the 
need  for  some  form  of  expression  on  the  student's  part 
of  the  information  imparted  in  the  instructions.  It  is 


8  INTRODUCTION 

a  well  understood  and  sound  principle  of  teaching  that 
we  do  not  really  know  a  thing  until  we  can  give  some 
expression  to  that  information,  or  in  other  words  make 
some  use  of  it.  Besides,  the  ability  to  "talk  pencil" 
is  a  very  valuable  acquisition  to  one  who  may  be  called 
upon  to  explain  the  meaning  of  a  drawing  or  give 
constructive  directions  to  others. 


Students  should  provide  themselves  with  a  good 
medium  or  soft  lead  pencil,  a  draftsman's  "B"  pencil  is 
a  very  suitable  one,  an  eraser,  a  pad  of  one-eighth  inch 
sectional  ruled  paper,  and  a  pad  of  cheap  drawing 
paper.  It  is  desirable  that  these  pads  be  about  the  size 
of  a  sheet  of  ordinary  typewriting  paper,  8l/2  inches  by 
11  inches. 


II.     KINDS  OF  DRAWINGS 


Drawings  are  of  various  kinds.  Plate  I  shows  sev- 
eral articles  represented  by  the  more  common  kinds 
of  drawings.  These  are  Perspective,  Isometric,  Cabi- 
net, Oblique  and  Orthographic.  The  perspective  is 
the  kind  of  drawings  used  for  ordinary  illustration 
work.  It  may  be  a  simple  outline  drawing  as  these  in 
the  first  column  of  Plate  I,  or  it  may  be  an  actual  pho- 
tographic reproduction  with  an  infinite  detail  and 
blending  of  light  and  shade.  It  is  a  drawing  of  an  ob- 
ject as  it  appears  to  the  eye  of  the  draftsman.  On  first 
thought,  this  would  seem  to  be  the  ideal  form  of  draw- 
ing. It  serves  to  show  how  an  object  looks,  but  it  is  de- 
defective  from  the  standpoint  of  showing  how  an  ar- 
ticle is  to  be  constructed. 

In  a  perspective  drawing  the  farther  from  the 
viewer  a  part  is,  the  smaller  it  is  on  the  drawing.  The 
cube  shown  in  Plate  I  illustrates  this  well.  Tho  it 
represents  a  one-half  inch  cube  all  edges  of  which  are 
one-half  inch  long,  there  is  but  one  line  on  the  perspec- 
tive drawing  of  it  which  measures  a  full  half  inch  in 
length.  This  characteristic  of  perspective  drawings 
makes  them  of  little  value  as  drawings  for  a  workman 
to  work  from,  as  there  is  no  way  he  can  scale  or  meas- 
ure the  drawing  for  sizes. 

Isometric  drawings  are  often  called  false  per- 
spective, or  shop  perspective  drawings  as  they  are  a 


form  of  imitation  perspective.  Isometric  drawings 
always  represent  the  object  with  three  surfaces,  usu- 
ally the  top  and  two  adjacent  sides,  all  inclined  at 
equal  angles  with  the  eye,  or — what  amounts  to  the 
same  thing — at  an  apparent  equal  angle  with  the  sur- 
face of  the  paper  on  which  the  drawing  is  drawn.  The 
lines  of  an  isometric  drawing  are  not  made  foreshort- 
ened by  the  distances  as  they  are  in  a  perspective 
drawing,  so  that  they  may  be  readily  scaled  by  a  work- 
man working  from  such  a  drawing.  Such  drawings 
are  much  more  easily  made  than  perspective  drawings 
and  have  the  advantage  of  giving  a  fair  pictorial  repre- 
sentation of  an  object  and  at  the  same  time  are 
drawings  from  which  a  workman  can  work. 

It  will  be  observed  that  isometric  drawings  give 
the  distorted  appearance  of  representing  the  object  as 
too  large  at  the  rear.  This  is  because  the  eye  expects 
things  on  a  drawing  to  appear  as  in  nature,  smaller  the 
farther  they  are  away,  or  technically,  foreshortened. 
This  distortion  is  very  apparent  in  the  Box  and  Cyl- 
inder represented  in  isometric  on  Plate  I  because 
these  are  long  objects. 

Cabinet  and  Oblique  drawings  are  very  similar. 
Both  represent  one  face  of  the  object  as  being  appar- 
ently parallel  with  the  surface  of  the  paper.  Lines 
which,  on  the  object  are  perpendicular  (  or  square) 


10 


BLUE  PRINT  READING 


'  with  this  surface  are  represented  as  extending  up  and 
to  the  right.  In  cabinet  drawings  these  lines  are  at 
an  angle  of  forty-five  degrees  (45°)  with  the  horizon- 
tal and  are  drawn  only  half  their  true  length  (fore- 
shortened.) In  oblique  drawings  these  lines  are  drawn 
at  an  angle  of  thirty  degrees  (30°)  with  the  horizontal 
and  are  drawn  their  full  length — or  in  other  words  are 
not  foreshortened. 

Cabinet  drawings  are  nearly  as  satisfactory  as  iso- 
metric drawings  from  a  pictorial  standpoint,  but  are 
somewhat  unsatisfactory  from  a  workman's  standpoint 
due  to  the  foreshortening  of  the  lines  drawn  at 
forty-five  degrees  (45°).  The  oblique  drawings  are 
more  satisfactory  from  a  workman's  standpoint  as  all 
lines  are  drawn  the  full  length.  They  are  the  easiest 
drawings  to  make  of  simple  objects,  but  they  make  a 
very  distorted  prctorial  representation  of  the  object. 

Orthographic  drawings  have  very  little  pictorial 
value  but  they  are  so  superior  to  all  other  forms  of 
drawings  from  the  standpoints  of  the  workman  and 
the  draftsman  that  probably  over  95%  of  all  working 
drawings  are  made  in  this  form.  Orthographic  draw- 
ings always  have  two  distinct  parts,  sometimes  three 
or  four.  One  of  these  parts  is  usually  called  the  plan 
or  top  view  and  represents  the  object  as  it  appears 
from  directly  overhead.  Another  is  known  as  the 


Elevation  or  Front  View  and  represents  the  ob- 
ject as  it  appears  directly  from  the  front.  The  Cube 
and  Box  in  Plate  I  are  represented  by  these  two  views. 
On  the  drawings  of  the  Cylinder  and  the  Hardie,  how- 
ever, no  plans  or  top  views  are  used  but  side  views 
or  side  elevations  supplements  the  front  views  or  ele- 
vations in  giving  information  which  is  not  given  in 
those  views.  Among  the  more  advanced  plates  in  the 
book  you  will  find  examples  of  drawings  where  it  takes 
three  and  perhaps  even  four  views  to  properly  repre- 
sent the  details  of  an  object. 

QUESTIONS   AND    PROBLEMS. 

1.  What  are  the  five  kinds  of  drawing  in  ordinary  use? 

2.  What   kind    of    drawing    is    represented   by   the    ordinary 
newspaper  cut? 

3.  Why  is  such  a  drawing  a  poor  one  for  a  workman  to  work 
from?    If  this  is  not  clear  to  you  try  taking  some  pictures 
from  a  furniture  advertisement  and  with  the  information 
that  chair  seats  are  18  inches  high  and  table  tops  32  inches 
high,  try  by  scaling  to  establish  other  dimensions   on  a 
chair  or  table. 

4.  How  many  pieces  of  wood  are  required  to  make  the  box 
as  shown  in  Plate  I? 

5.  With   a  rule   determine  what  are  the   overall   dimensions 
of  the  Box  assuming  it  to  be  drawn  full  size? 

6.  How  deep  is  the  hole  in  the  Cylinder? 

7.  How  long  is  the  shank  of  the  Hardie? 

8.  Which  is  the  only  drawing  from  which  you  can  accurately 
get  the  answer  to  question  7,  and  why? 


DIFFERENT    KINDS     OF    DRAWING 


PERSPECTIVE. 


ISOMETRIC 


CABINET 


OBt-IQUE. 


ORTHOGFiA  fH/C 


Plan 


Elevation 


•r  Front 
View 


Side 


Front 


I 

Q: 
I 


Plate  I 


11 


III.     THE  THEORY  OF  ORTHOGRAPHIC  PROJECTION 


If  one  should  take  a  pane  of  glass  and  hold  it 
steadily  between  his  eye  and  some  object  he  desired 
a  picture  of,  he  might  trace  on  the  glass  an  outline  of 
the  object  and  this  tracing  would  be  an  accurate  per- 
spective drawing.  In  Fig.  I,  Plate  II,  is  a  perspective 
drawing  illustrating  this.  A  represents  the  eye  of  the 
viewer,  B  the  glass,  C  the  object,  and  D  the  tracing 
on  the  glass  of  the  object  as  it  appears,  to  the  viewer. 
In  other  words,  D  is  the  perspective  drawing  of  the 
object.  Technically  what  we  have  represented  as  a 
piece  of  glass,  is  a  picture  plane.  A  plane  is  defined 
as  that  which  has  length  and  breadth  but  no  thick- 
ness. It  is  of  course  not  a  material  object,  but  it  is 
convenient  to  use  material  objects,  as  glass  or  a  sheet 
of  paper  by  which  to  represent  it. 

In  practice  it  is  impractical  to  make  drawings  by 
the  method  illustrated  in  Fig.  I,  so  draftsmen  use  a 
sheet  of  paper  fastened  to  a  drafting  board,  but  the 
drawings  are  made  exactly  in  conformity  with  the 
theoretical  method  just  discussed. 

In  the  preceding  chapter  we  pointed  out  that  per- 
spective drawings  were  impractical  as  working  draw- 
ings, due  to  the  fact  that  as  the  distance  of  the  object 
from  the  eye  of  the  viewer  increased  the  smaller  it 
appeared.  This  can  be  seen  by  imagining  the  object 
in  Fig.  I  to  be  at  a  greater  distance  away  from  the  eye 

m 


than  shown.  The  tracing  on  the  picture  plane  would 
decrease  in  size  as  the  distance  increased.  The  same 
result  would  occur  if  the  distance  between  the  eye  and 
the  picture  plane  were  lessened.  If  the  eye  were  di- 
rectly against  the  picture  plane,  the  tracing  would  be- 
come only  a  point.  If  it  were  the  object  that  were 
placed  against  the  picture  plane  and  the  eye  were  at 
a  distance  the  tracing  would  appear  the  full  size  of  the 
object  itself. 

Now,  because  of  the  practical  impossibility  of  scal- 
ing a  perspective  drawing,  as  brought  out  by  the  dis- 
cussion in  this  and  the  preceding  chapter,  and  because 
a  perspective  drawing  is  a  very  complicated  kind  to 
draw — especially  where  it  is  of  an  object  being  designed 
and  the  object  cannot  be  looked  at,  draftsmen  have 
developed  the  system  known  as  orthographic  drawing 
or  orthographic  projection. 

The  theory  on  which  orthographic  drawings  are 
made  is  a  little  more  complicated  than  that  for  per- 
spective drawings,  but  the  drawings  are  vastly  sim- 
pler, for  the  draftsman  and,  if  he  thoroly  understands 
the  theory,  for  the  workman  also.  The  success  of  this 
entire  course  depends  very  largely  upon  the  student 
mastering  the  theory  of  orthographic  drawing.  Be- 
cause of  its  importance  it  has  been  worked  out  step 


12 


!Q 


Plate  II 


13 


14 


BLUE  PRINT  READING 


by  step  with  all  of  Plate  II  devoted  to  developing  this 
theory. 

In  the  preceding  chapter,  in  the  discussion  of  ortho- 
graphic drawing,  it  was  pointed  out  that  an  ortho- 
graphic drawing  was  made  up  of  two,  sometimes  more, 
"views"  of  an  object.  The  use  of  the  word  "view"  is 
not  correct  if  used  in  the  sense  that  it  was  used  while 
discussing  Fig.  1.  In  Fig.  2  is  shown  the  same  object 
and  the  same  picture  plane  as  in  Fig.  1.  The  tracing  on 
the  picture  plane,  however,  is  a  true  orthographic 
drawing  in  that  it  is  the  actual  size  of  the  object  itself. 
Note  that  the  position  of  the  eye  of  the  viewer  is  not 
fixed.  When  a  certain  point  on  the  object  is  to  be 
traced  on  the  picture  plane  the  eye  is  moved  so  that 
it  is  directly  opposite  the  point  on  the  object.  A  better 
way  to  state  this  fact  is,  perhaps,  that  the  line  of  sight 
must  be  kept  perpendicular  or  "square"  with  the 
picture  plane.  This  makes  the  lines  of  sight  from  all 
points  on  the  object  parallel  with  one  another,  and  the 
tracing  on  the  picture  plane  the  full  size  of  the  object. 
Still  another  way  to  think  of  orthographic  drawing  is 
not  to  think  in  terms  of  views  and  tracings  at  all,  but 
simply  as  a  projection  of  the  outline  .of  the  object  to 
the  picture  plane  by  projection  lines  perpendicular  to 
the  picture  plane.  This  is  the  way  the  draftsman  usu- 


ally thinks  and  for  this  reason  he  usually  uses  the  term 
orthographic  projection  rather  than  orthographic  draw- 
ing or  tracing. 

Reference  to  Fig.  2  shows  that  tho  the  projection, 
or  tracing,  on  the  picture  plane  shows  the  height  and 
width  of  the  object  it  does  not  show  the  thickness.  It 
requires  another  view  or  projection  to  accomplish  this 
just  as  it  required  two  in  the  orthographic  drawings  on 
Plate  I. 

Fig.  3  shows  several  articles  located  beyond  two 
picture  planes — one  located  vertically  before  the  ob- 
jects and  the  other  extending  horizontally  above  the 
objects.  On  these  planes  are  projections  of  the  objects. 
The  projection  lines  (or  lines  of  sight,  if  you  prefer) 
are  shown  by  fine  lines  of  alternate  long  and  short 

dashes    ( ).      Fig.    4    shows 

these  two  planes  laid  out  flat  as  a  draftsman  would 
represent  them  on  his  drawing.  The  top  views  (or 
horizontal  projections,  since  they  are  projections 
on  the  horizontal  plane)  are  located  directly  above  the 
front  view. 

Many  objects  can  not  be  fully  shown  by  two  pro- 
jections so  that  it  is  frequently  necessary  to  add  a  side 
projection.  Fig.  5  shows  an  object  back  of  three 
picture  planes  and  with  projections  of  the  object  on 
the  planes.  Fig.  6  shows  the  planes  opened  up  so 


THE  THEORY  OF  ORTHOGRAPHIC  PROJECTION 


15 


that  the  projections  appear  in  the  proper  position  they 
should  appear  in  a  drawing.  Fig.  7  shows  the  three 
projections  of  the  object  as  a  draftsman  would  ordi- 
narily represent  it  with  the  planes  and  part  of  the  ex- 
tension lines  omitted. 

In  practice  a  draftsman  never  draws  in  the  planes. 
He  simply  shows  the  two  projections  and  leaves  the 
reader  to  imagine  the  planes,  but  he  always  thinks  of 
his  drawings  as  being  drawn  on  planes  so  it  is  neces- 
sary that  the  reader  think  of  them  in  the  same  way. 
Often  the  draftsman  omits  the  extension  lines  also, 
more  often  he  draws  them  in  pencil  but  does  not  ink 
them  so  that  they  do  not  appear  on  a  blueprint. .  Note 
that  the  extension  lines  (Fig.  4)  are  an  aid  in  locating 
the  same  point  in  the  different  views.  In  the  projec- 
tions of  the  second  article  in  Fig.  4,  an  angle  block, 
the  extension  line  locates  the  lower  end  of  the  brace 
piece.  It  is  worth  while  to  keep  in  mind  that  identical 
points  on  the  different  views  of  a  drawing  always  are 
directly  in  line  up  and  down  or,  in  case  of  front  and 
side  views,  horizontally.  On  complicated  drawings  it 
often  is  a  great  aid  in  reading  them  to  lay  a  straight 
edge  across  from  view  to  view  to  locate  identical  parts 
on  the  different  views. 

Instead  of  hinging  the  side  plane  (profile  plane  it 
is  sometimes  called)  to  the  front  or  vertical  plane  as 

2 


shown  in  Fig.  7,  a  draftsman  sometimes  hinges  it  to 
the  top  or  horizontal  plane.  Fig.  8  shows  the  result- 
ing arrangement  of  views  while  the  planes  themselves 
have  been  omitted.  Such  an  arrangement  often  saves 
space  on  a  drawing. 

The  arrangement  of  placing  the  horizontal  plane 
above  the  object  and  the  vertical  plane  in  front  is  in 
accord  with  the  best  modern  practice,  but  it  is  well  to 
know  that  it  was  once  customary  to  use  the  arrange- 
ment shown  in  Fig.  9.  In  this  the  vertical  picture 
plane  is  placed  behind  the  object  and  the*  horizontal 
picture  plane  below.  The  extension  lines  extend  back 
or  downward  to  the  picture  planes.  When  laid  out  flat 
as  in  Fig.  10  it  will  be  observed  that  the  top  view 
comes  below  and  the  front  view  comes  above.  As  some 
draftsmen,  especially  among  architects,  still  use  this 
arrangement  it  is  well  to  know  how  to  look  upon  it. 

Fig.  11  shows  a  practical  application  of  orthogra- 
phic projection  as  applied  to  architecture,  representing 
the  horizontal,  vertical  and  profile  projections  of  a 
house,  or  in  the  terminology  more  common  as  applied 
to  houses,  roof  plan,  front  elevation  and  side  eleva- 
tion. Note  that  the  draftsman  has  in  this  followed  the 
very  common  custom  of  omitting  all  extension  lines, 
depending  upon  the  proximity  and  location  of  the  vari- 
ous views  to  show  that  they  belong  together. 


16 


BLUE  PRINT  READING 


QUESTIONS    AND    PROBLEMS. 


1.  Take  a  sheet  of  sketch  paper  and  fold  it  at  the  center 
so  that  its  two  parts  are  at  right  angles  like  the  vertical 
and  horizontal  picture  planes  in  Fig.  3.     Place  these  over 
a  small  rectangular  block  or  box  as  the  object  //  is  placed 
in  Fig.  3  and  roughly  sketch  the  top  and  front  views.     It 
should  give  views  similar  to  A  Fig.  4,  but  of  a  size  de- 
pending upon  the  object  used. 

2.  Use  Section  ruled  paper.     Draw  a  line  down  the  middle 
lengthwise  of  the  sheet  to  represent  the  line  separating 
the  two  planes.    Turn  the  sheet  so  this  line  is  horizontal 
— runs  right  and  left — and  draw  both  the  top  and  front 
views  of  a  block  1  inch  x  2  inch  x  3  inch,  getting  your 
measurements  by  following  the  one  inch  square  lines  on 
your  paper.     Draw  these  free  hand.     Note  the  different 
arrangement  or  views  resulting  from  different  positions 
in  which  you  assume  the  block  to  lie.    Draw  six  complete 
drawings   (both  top  and  front  views)   showing  the  block 
in  different  positions. 

3.  Represent  by  two  views  as  before  a  block  one  inch  high, 
the  top  of  which  is  154  inches  square.  After  completing  the 
block  represent  a  silver  dollar  as  being  on  the  block.  Study 
carefully  D,  Fig.  4  and  Fig.  3.     After  completing  both 
top  and  front  views  of  the  dollar  represent  a  smaller  coin 
as  being  on  the  dollar.    Note  E,  Figs.  3  and  4. 

4.  Draw   plan   and   elevation    (top   and    front    views)    of    a 
cylinder  1%  inches  in  diameter  and  2  inches  high.   When 


complete  represent  a  hole  thru  it  1  inch  in  diameter.  Note 
carefully  the  representation  of  holes  in  E,  Fig.  4,  and  also 
the  orthographic  drawing  of  the  cylinder  on  Plate  I. 

5.  Draw  plan,  elevation  and  profile  (three  views)  of  a  block 
\Y2  inches  x  2  inches  x  2l/2  inches,  as  in  Fig.  8.     Repre- 
sent a  groove  94  inch  wide  and  *4  inch  deep  as  extending 
entirely  around  the  block. 

6.  Make  three  views  of  object  B,  Fig.  3,  increasing  the  size 
to  more  convenient  dimensions. 

7.  Make  three  views  of  object  C,  increasing  the  size  to  more 
convenient  dimensions. 

8.  Why  would  no  advantage  be  derived  from  making  a  third 
view  of  objects  D  and  E,  Figs.  3  and  4? 

9.  What  is  brought  out  in  Figs.  6,  7  and  8  by  the  third  or 
profile  view  that  is  not  clear  from  the  other  two  views? 

10.  Sketch  a  three  view  drawing  of  a  block  1  inch  x  2  inches 
x  3  inches.  Mark  each  of  the  block's  eight  corners  by  let- 
ters a,  b,  c,  d,  e,  f,  g,  and  h.  Locate  each  of  these  eight 
corners  in  all  three  views.  Better  use  a  small  block  or 
box  with  the  corners  marked,  as  a  model.  Be  sure  each 
letter  appears  in  all  three  views.  Where  two  letters  come 
in  the  same  place  on  a  view  make  the  back  letter  a  small 
one  and  the  other  a  capital  letter. 


IV.     MEANING  OF  VARIOUS  KINDS  OF  LINES 


The  student  has  doubtless  noticed  that  there  is 
quite  a  variety  of  lines  used  in  mechanical  drawings. 
Each  kind  of  line  has  its  own  meaning  when  on  a 
drawing.  Fig.  1,  Plate  III,  has  five  different  kinds  of 
lines  used  in  showing  a  simple  square  block  with  a 
square  hole  halfway  thru  it.  There  are  fine  solid  lines, 
heavy  broad  solid  lines,  lines  of  dashes,  lines  of  short 
dashes  and  a  line  composed  of  alternate  two  dots  and 
a  dash.  Let  us  see  what  these  various  lines  mean. 

The  fine  solid  line  is  used  to  represent  (1)  an  edge 
where  two  surfaces  come  together,  as  the  ridge  line 
on  the  roof  plan  of  the  house  on  Plate  II  (Fig.  11); 
(2)  where  it  represents  a  flat  surface  turned  edgeways 
to  the  picture  plane,  as  the  edge  of  the  block  A,  Fig.  4, 
Plate  II  and  in  Fig.  1,  Plate  III.  (3)  and  where  it 
represents  that  part  of  curved  surface  which  is  edge 
ways  to  the  picture  plane,  as  the  lines  a  and  a'  as  on 
the  elevation  of  the  cylinder  in  Fig.  4,  Plate  II. 

Another  line  in  Fig.  I,  Plate  III,  is  the  heavy  broad 
line.  It  is  called  a  shade  line  and  is  a  convention- 
alized shadow.  On  all  kinds  of  drawing,  the  draw- 
ing a  viewer  is  looking  at  is  supposed  to  be  held  verti- 
cally before  the  eyes,  and  the  light  is  supposed  to  come 
over  the  left  shoulder  of  the  viewer.  Shade  lines  rep- 
resent such  edges  as  separate  surfaces  turned  towards 
the  light  from  those  turned  aw^y  from  the  light — in 
other  words  they  separate  light  from  dark  surfaces. 


Shade  lines  are  not  used  by  some  draftsmen  and  not  in 
every  drawing  by  all  draftsmen.  Shade  lines  are  a 
little  troublesome  to  put  in  on  a  drawing  but  add  to 
the  appearance  of  a  drawing  and  help  to  bring  out 
the  meaning.  Note  that  in  Figs.  1  &  2,  Plate  III,  the 
top  views  are  identical  except  for  the  shade  lines.  The 
use  of  these  shade  lines  emphasizes  the  fact  that  the  in- 
side square  on  one  view  represents  a  hole  while  in  the 
other  it  represents  a  projection.  So  clearly  does  it 
emphasize  this,  that  if  there  were  no  occasion  to  show 
how  deep  the  hole  is  or  how  high  the  projection  is,  the 
front  views  might  be  entirely  dispensed  with.  Shade 
lines  are  very  largely  used  for  drawings  of  U.  S.  pat- 
ents. 

Two  other  lines  on  Fig.  I,  Plate  III,  are  the  broken 
or  longer  dashed  lines  and  the  dotted  or  short  dash 
lines.  The  longer  dashes  are  used  as  extension  lines, 
that  is  lines  extending  from  view  to  view  to  locate 
the  same  part  on  different  views.  As  stated  before, 
extension  lines  are  often  omitted  by  draftsmen  where 
used  for  this  purpose.  Extension  or  dashed  lines  are 
also  used  to  connect  parts  of  the  drawing  with  the 
ends  of  dimension  lines.  These  dimension  lines  will 
be  discussed  later. 

The  dotted  lines  or  short  dash  lines  represent  a 
hidden  edge  as  the  sides  and  bottom  of  the  hole  in  the 
elevation  drawing,  Fig.  I,  Plate  III.  In  Fig.  6  the 


17 


18 


BLUE  PRINT  READING 


dotted  line  shows  the  bottom  of  the  depression. 

The  line  consisting  of  alternating  two  dots  and  a 
dash  and  extending  entirely  thru  both  views  of  Fig.  1, 
is  a  center  line.  Center  lines  divide  views  which  are 
symmetrical.  They  are  drawn  in  a  variety  of  ways, 
tho  the  way  shown,  or  one  dot  and  a  dash  are  the 
most  usual  ways.  The  center  lines  of  Figs.  8,  10,  and 
11  are  examples  of  the  dash  alternating  with  a  single 
dot.  In 'Fig.  2,  the  center  line  has  tw6  dots  alternating 
with  a  dash.  Center  lines  are  occasionally  drawn  solid 
as  in  Fig.  3.  They  are  always  drawn  fine,  often  the 
finest  line  on  the  drawings.  Whatever  way  they  may 
be  represented  they  always  represent  an  axes  of  sym- 
metry and  extend  beyond  the  bounds  of  the  drawings. 
Frequently  a  center  line  is  circular  as  in  Fig.  7,  then 
it  connects  the  centers  of  several  similar  parts — in  this 
case  several  holes.  Drill  holes  and  usually  all  circular 
parts  of  drawings  are  crossed  at  the  centers  by  two 
intersecting  center  lines  at  right  angles  to  one  another 
—Fig  7. 

Another  kind  of  lines  also  known  as  shade  lines  is 
shown  in  Figs.  4,  5  and  6.  These  are  the  fine  lines 
drawn  close  together  to  give  an  appearance  of  the 
surface  being  curved.  It  is  evident  that  Fig.  4  repre- 
sents a  cylinder  tho  but  one  view  is  shown.  Fig.  5  is 
just  as  plainly  a  sphere  supported  by  a  circular  shaft 


from  a  circular  base.  Tho  the  saving  of  a  view  would 
seem  to  justify  frequent  use  of  such  lines  on  drawings, 
draftsmen  do  not  generally  use  them  except  on  patent 
office  drawings,  as  these  lines  are  often  in  the  way  of 
hidden  edge  and  other  lines. 

A  line  or  rather  an  arrangement  of  lines  similar  to 
shade  lines  is  that  shown  in  the  drawing  of  the  spool, 
Fig.  8.  These  are  the  parallel  diagonal  lines  in  the 
right  hand  "view."  These  parallel  lines  indicate  that 
this  is  not  an  elevation  or  outside  view,  but  is  a  cross 
section  or  view  of  the  object  after  it  has  been  cut  on 
the  center  line.  These  parallel  lines  can  be  considered 
as  the  marks  of  the  saw  used  in  cutting  it.  These  sec- 
tion lines  are  very  frequently  made  freehand  by  archi- 
tectural draftsmen  especially  where  they  represent  a 
cross  section  of  wood.  Often  a  draftsman  desires  to 
show  the  kind  of  material  at  the  same  time  he  is  show- 
ing a  section  view.  Then  instead  of  using  the  kind 
of  lines  in  use  in  Fig.  8,  he  usss  a  kind  of  line  or  line 
arrangement  which  draftsmen  have  adopted  as  indicat- 
ing the  kind  of  material  he  wishes  to  represent.  Fig.  9 
is  a  chart  showing  cross  sectior.ings  in  common  use  for 
different  materials.  Unfortunately,  tho  these  sections 
are  in  common  use,  they  are  not  recognized  as  uni- 
versal standard  conventions  and  for  that  reason  it  is 
not  safe  to  depend  upon  them  unless  a  note  on  the 


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Plate  III 


19 


20 


BLUE  PRINT  READING 


drawing  names  the  material,  or  the  convention  is  made 
standard  by  the  drafting  office  from  which  the  draw- 
ing comes. 

More  attention  is  given  to  the  matter  of  sections  in 
a  later  part  of  the  course. 

Arrow  lines  are  conspicuous  lines  on  most  working 
drawings.  They  may  serve  to  lead  the  eyes  from  some 
note  to  that  part  of  the  drawing  to  which  the  note  ap- 
plies, as  the  notes  on  Figs.  7  and  10.  Such  arrow  lines 
may  be  drawn  in  freehand  as  is  the  one  leading  from 
the  word  "drill"  in  Fig.  7,  or  with  a  straight  ruled  line 
as  the  one  leading  from  the  words  "cored  hole".  The 
arrow  barbs,  see  Fig.  10,  are  drawn  single  or  double 
as  may  please  the  draftsman,  and  without  any  particu- 
lar meaning  being  attached  to  them. 

In  Fig.  10  arrows  are  used  for  another  common 
purpose.  They  show  the  direction  of  movement  of  a 
moving  part,  in  this  case  the  direction  of  the  rotation 
of  the  pulleys  and  belt.  Arrows  for  this  purpose  are 
very  frequently  drawn  with  feather  lines  on  the  rear 
end  of  the  shaft. 

The  arrow  arrangement  shown  in  Fig.  11  is  fre- 
quently found  with  the  drawing  title  on  maps,  and  lot 
and  foundation  plans.  It  indicates  the  four  principal 
points  of  the  compass.  On  a  foundation  plan  it  readily 
shows  the  direction  a  building  is  to  face.  The  initial 


letters  are  frequently  omitted  as  the  arrow  invariably 
points  directly  north. 

Another  use  to  which  arrow  lines  are  put  is  shown 
in  Fig.  12.  It  is  to  show  dimensions.  A  dimension  line 
ordinarily  has  an  arrow  at  each  end  and  with  the 
length  of  the  dimensions  stated  by  the  numerals  near 
the  center  of  the  line.  The  shaft  of  a  dimension  line 
is  made  in  various  ways,  the  more  common  of  which 
is  a  fine  solid  line  broken  for  the  numeral  at  the  center. 
Other  ways  of  making  them  will  be  discussed  in  a 
following  chapter.  Where  one  end  of  a  dimension  line 
is  ended  by  a  small  freehand  circle,  as  the  1"  dimen- 
sion in  Fig.  12,  it  indicates  that  the  dimension  is  the 
radius  of  an  arc  of  which  the  small  circle  is  the  center. 
When  a  dimension  line  is  outside  the  view  proper  as 
the  two  2"  and  l%"  dimensions  in  Fig.  12,  short 
broken  extension  lines  connect  the  tips  of  the  ar- 
rows with  the  drawing  to  which  the  dimension  refers. 
When  these  are  drawn  by  a  careful  draftsman  they 
do  not  actually  touch  the  drawing. 

This  perhaps  is  an  opportune  place  to  remark  that 
the  grammar  of  drawing  is  as  frequently  violated  as  is 
the  grammar  of  English,  and  we  must  learn  to  under- 
stand improperly  drawn  drawings,  just  as  necessity 
requires  us  to  understand  the  intended  meaning  and 
not  the  literal  meaning  of  our  fellow  workmen. 


MEANING  OF  VARIOUS  KINDS  OF  LINES 


21 


QUESTIONS    AND    PROBLEMS. 


1.  What  drawing  in  Plate  I  has  lines  showing  hidden  edges? 

2.  By  what  is  it  clear  that  the  hole  in  the  block  shown  in 
Fig.  1,  Plate  III,  is  not  entirely  thru  the  block  as  is  the 
hole  in  the  cylinder  in  Plate  I? 

3.  How  deep  are  the  holes  shown  in  Figs.  6,  7  and  8? 

4.  Were  it  not  for  the  name,  how  would  we  know  that  the 
article  shown  in  Fig.   12  would  hold  matches? 

5.  How  many  pieces  to  the  Match  Holder? 

6.  Using  a  sheet  of  section  ruled  paper  to  aid  in  getting  the 
dimensions   easily  and  correctly  draw   (1)   a  block  with 
a  top   V/t  inches  by  3l/j  inches,  height   or  thickness   of 
block  to  be  1  inch.    The  block  to  be  represented  as  having 
a  1   inch  by  y/t  inch  side  towards  the  draftsman  rather 
than  the  end.     (2)     Now,  show  a  y2  inch  square  hole  ex- 
tending through  the  block,  located  l/2  inch  from  the  left 
end,  otherwise  in  the  center  of  the  block.     Use  necessary 
dotted  lines  to  show  that  the  hole  is  entirely  through  the 
block.    (3)     Show  a  l/t  inch  square  hole  similar  to  the  one 
just  made  except  that  it  is  but  l/2  inch  deep.     (4)     Locate 
a  Y2  inch  cube  in  the  center  of  the  remaining  space  on  top 


of  the  large  block.   (5)   Put  in  a  center  line  on  the  axis  of 
symmetry  and  dimension  the  entire  drawing  fully. 

7.  (1)     On  section  ruled  paper,  redraw  at  a  convenient  size 
the  objects  on  Figs.  3  and  4  of  Plate  II,  adding  side  views 
and  using  shade  lines. 

8.  Draw  the   cylinder  in   Fig.   3,   Plate   II,   but   instead   of 
showing  it  by  but  one  view  and  the  kind  of  shade  lines 
used  in  this  drawing,  show  it  by  a  top  and  front  view 
without  shade  line.    Use  proper  center  lines.    (2)    Change 
drawing  so  that  it  represents  a  cylindrical  open  top  box 
with  y&  inch  thick  walls. 

8.     Draw  Fig.  5,  Plate  III,  omitting  the  shade  lines  but  add 
a  top  view  with  the  necessary  hidden  edge  lines. 

10.  Represent  Fig.  6  with  a  third  "view"  in  section  as  is  the 
spool  in  Fig.  8.     Add  overall  dimensions. 

11.  Draw  a  number  of  simple  objects,  representing  them  by 
necessary  center  lines,  hidden  edge  lines,  etc.     Use  three 
views  if  necessary.     Use  shade  lines  only  on  very  simple 
objects.    Good  models  are  ink  well,  tumbler,  table  knife, 
thimble,  pill  box,  bolt,  nut,  etc. 


V.     FORESHORTENED  LINES,  INCLINED 

Draftsmen  usually  represent  the  objects  they  draw 
so  placed  that  the  surfaces  of  the  object  are  parallel  to 
the  picture  planes,  as  in  the  rectangular  object  in  Fig. 
I,  Plate  IV.  This  is  not  always  possible  or  convenient. 
Figs.  2  and  3  show  the  same  object  but  turned  so  that 
the  front  face  is  no  longer  parallel  to  the  front  or 
vertical  picture  plane.  The  shaded  surfaces  in  Fig.  2 
are  an  unusual  aid  to  the  reader  on  the  draftsman's 
part.  He  usually  leaves  the  surfaces  unshaded  as  in 
Figs.  1,  3  and  4,  for  to  a  skilled  reader  of  drawings 
such  aids  to  understanding  a  drawing,  are  unnecessary. 

By  the  dimensions  on  the  elevation  of  Fig.  1,  we 
note  that  the  width  of  the  object  is  one-half  inch,  but  if 
the  reader  should  try  testing  the  width  of  the  eleva- 
tions of  the  same  object  in  Figs.  2  and  3,  he  would  dis- 
cover that  they  do  not  measure  one-half  inch.  The 
more  a  surface  or  a  line  is  inclined  to  a  picture  plane, 
the  smaller  it  becomes.  This  shortening  of  surfaces 
and  lines  due  to  inclination  is  known  as  Foreshorten- 
ing, and  appears  somewhere  in  almost  every  drawing. 

In  Fig.  4  the  same  object  is  shown  as  before  but 
this  time  the  inclination  is  towards  the  horizontal 
picture  plane. 

It  will  be  evident  by  inspecting  and  a  little  scaling 
that  a  workman  who  attempts  to  scale  a  drawing,  must 
carefully  avoid  trying  to  scale  a  line  which  is  fore- 

22 


SURFACES,  AUXILIARY  PROJECTIONS 

shortened.  A  draftsman  never  places  a  dimension  on  a 
line  that  is  foreshortened. 

In  Fig.  5  is  shown  a  very  practical  and  frequent 
example  of  foreshortening.  It  represents  the  plan  and 
elevation  of  a  small  building  having  its  door  and  porch 
turned  at  45  degrees  to  the  main  parts  of  the  house. 
Note  that  all  the  lines  on  the  porch  except  the  verti- 
cal ones,  are  foreshortened  in  the  elevation.  If  this  is 
not  clear  try  comparing  the  length  of  the  lines  repre- 
senting the  front  and  side  of  the  porch  floor  in  the  two 
views.  It  will  be  noted  that  these  lines  will  scale 
shorter  in  the  elevation.  This  is  because  one  end  of 
these  lines  is  nearer  the  vertical  picture  plane  than  the 
other,  or  in  other  words  nearer  to  the  viewer,  but  in 
the  plan  or  top  view  these  lines  are  parallel  with  the 
horizontal  picture  plane. 

In  Fig.  6  is  seen  another  example  of  foreshortening 
in  the  drawing  of  the  Angled  Bearing  Support.  The 
effect  of  foreshortening  is  particularly  noticeable  in 
the  front  elevation  representation  of  the  circular  open- 
ing where  it  appears  not  as  a  circle  but  as  an  ellipse. 
The  side  projection  of  this  drawing  is  not  like  any 
represented  heretofore.  In  fact  it  is  not  a  side  projec- 
tion but  what  is  called  an  auxiliary  projection.  A 
true  side  projection  is  a  projection  on  a  plane  at 
right  angles  to  both  the  horizontal  and  vertical  planes. 


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23 


BLUE  PRINT  READING 


An  auxiliary  projection  is  a  projection  on  a  plane  per- 
pendicular to  but  one  of  these,  and  is  usually  parallel 
to  some  surface  on  the  object  itself  as  in  this  case,  the 
plane  is  parallel  to  the  circular  end  of  the  bearing. 

In  Fig.  7  is  shown  the  arrangement  of  planes  neces- 
sary to  secure  an  auxiliary  projection  parallel  to  the 
side  of  the  object.  Note  that  the  auxiliary  plane  is 
placed  so  it  is  parallel  with  the  face  of  the  pyramid. 
This  results  in  giving  a  projection  of  this  face  exactly 
the  size  of  the  face  of  the  object.  This  is  not  the  case 
in  the  front  projection,  where  because  the  lower  end 
of  the  front  face  is  nearer  the  plane  than  the  top,  the 
surface  appears  slightly  foreshortened  in  the  projec- 
tion. Were  a  workman  trying  to  make  this  pyramid 
out  of  sheet  metal  this  auxiliary  projection  would  be 
the  only  one  on  which  he  could  get  a  correct  layout  for 
cutting  his  metal.  If  he  made  his  layout  from  a  fore- 
shortened projection  he  would  not  get  the  correct 
shape. 

Note  that  the  auxiliary  projection  in  Fig.  7  shows 
not  only  the  surface  towards  the  auxiliary  plane,  but 
also  two  other  surfaces.  These  two  other  sides  are  too 
much  foreshortened  to  be  of  any  value,  so  draftsmen 
often  omit  from  such  projections;  such  parts  of  a  draw- 
ing as  they  have  no  need  for.  The  draftsman  has  done 
this  in  the  auxiliary  projection  of  the  church  steps,  in 


Fig.  8.  The  plan  and  elevation  show  all  that  is  neces- 
sary for  the  construction  of  the  steps  except  that  no 
parts  of  the  plan  or  elevation  represent  the  crosses  in 
their  true  shape.  Therefore,  the  draftsman  has  had  to 
put  in  an  auxiliary  projection  to  show  the  true  shape 
and  size  of  one  of  these  crosses.  If  he  had  drawn  a 
complete  projection  of  the  steps  it  would  have  entailed 
as  much  drawing  as  for  either  his  plan  or  front  eleva- 
tion, so  he  has  drawn  an  abbreviated  auxiliary  pro- 
jection showing  only  the  end  of  the  buttress  which 
fully  serves  his  purpose. 

Occasionally  auxiliary  projections  are  the  only  sat- 
isfactory way  of  representing  an  object.  Figs.  9  and  10 
show  an  iron  forging  represented  in  two  ways.  In  Fig. 
10  the  common  arrangement  of  a  horizontal  projection 
is  omitted  and  two  partial  auxiliary  projections  take 
its  place  and  with  much  more  satisfactory  results.  The 
horizontal  projection  in  Fig.  9  has  the  most  important 
parts  foreshortened,  the  drill  holes  appear  elliptical 
and  the  eye  is  not  represented  as  being  a  true  ring  as  it 
is  intended  to  be.  By  using  the  two  partial  auxiliary 
projections,  as  in  Fig.  10,  the  drill  holes  are  shown  to 
be  round  at  their  proper  distances  apart,  and  the  eye 
of  the  rod  is  shown  to  be  a  true  round  ring. 

Note  the  draftsman's  use  of  a  break  to  prevent  his 
having  to  draw  more  of  the  projection  than  he  had 
need  for. 


FORESHORTENED  LINES,  INCLINED  SURFACES,  AUXILIARY  PROJECTIONS 


25 


Closely  related  to  the  preceding  discussions  is  the 
matter  of  what  combinations  and  position  of  surfaces 
make  line  on  a  drawing.  The  rule  is, — the  boundaries 
of  surfaces,  perpendicular  edges,  and  distinct  inter- 
sections of  surfaces  are  represented  by  lines  on  the 
picture  planes. 

Only  such  parts  of  an  object  as  come  within  this 
rule  can  be  represented  on  a  drawing  by  lines  unless 
shading  of  some  sort  be  added.  This  is  rarely  practical 
for  working  drawings.  Fortunately  the  application  of 
the  rule  seldom  leaves  any  parts  of  the  object  unrepre- 
sented on  the  drawing  by  lines  tho  it  is  frequently 
necessary  to  consider  two  projections  or  views  at  the 
same  time  in  order  to  be  sure  of  a  surface. 

The  various  kinds  of  ribbed  pieces  or  moldings 
represented  in  the  drawings  grouped  under  Fig.  11 
illustrate  the  application  of  the  above  and  also  em- 
phasize that  caution  must  be  observed  not  to  depend 
upon  one  view  in  reading  a  drawing.  All  the  lines,  ex- 
cept of  course  the  center  line,  of  the  vertical  projec- 
tions (front  views)  illustrate  all  three  classes  of  the 
rule — (1)  boundaries  of  surfaces,  (2)  perpendicular 
edges,  (3)  distinct  intersection  of  surfaces.  The  lines 
a',  and  b',  of  drawing  A  also  represent  all  these  classes. 
Lines  c,  d,  and  e,  of  drawing  B  illustrate  clause  3 — 
distinct  intersection  of  surfaces.  Note  that  object  C 


is  the  same  as  B  except  that  there  is  no  distinct 
intersection  of  surfaces.  The  horizontal  projection 
of  C  is  an  excellent  illustration  of  the  necessity  of 
always  considering  all  projections  of  a  drawing  at 
a  time.  If  one  were  to  consider  the  horizontal  projec- 
tion of  C  only  he  would  be  very  likely  to  come  to  the 
erroneous  conclusion  that  it  represented  a  flat  surface. 
There  is  no  way  for  the  draftsman  to  show  by  lines 
that  this  is  not  a  flat  surface  except  by  depending  upon 
the  other  projection  or  by  resorting  to  shade  lines  or 
other  means  of  shading.  As  the  vertical  projection — if 
the  reader  does  not  neglect  to  take  it  into  considera- 
tion— makes  the  true  shape  clear,  the  draftsman  would 
seldom  resort  to  shading,  as  he  has  not  resorted  to  it 
in  this  drawing.  Draftsmen  usually  assume  that  those 
who  are  to  read  their  drawings  understand  drawings 
as  well  as  they  do.  The  lines  h',  and  y',  drawing  D  illu- 
strate clause  (2) — perpendicular  edges.  They  do 
not  represent  distinct  intersections  nor  boundaries 
of  surfaces.  Lines  h',  i',  j',  and  k'  of  drawing  B 
also  illustrate  lines  representing  perpendicular  edges. 
These  edges  are  perpendicular  only  at  places  h, 
i,  j  and  k  but  since  they  are  perpendicular  at  these 
places  they  are  represented  by  lines  on  the  other  pro- 
jection. As  illustrated  by  lines  /'  and  k'  hidden  edge 
lines  are  subject  to  the  same  rules  as  visible  lines. 


BLUE  PRINT  READING 


QUESTIONS  AND   PROBLEMS. 


1.  What  do  the  dotted  lines  on  the  elevations  of  Figs.  2  and 
3  represent? 

2.  Has  the  revolving  of  the  object  in  Figs.  2  and  3  affected 
the  height  any?     Has  it  affected  the  thickness  and  width 
in  the  plans  (top  views)? 

3.  How  many  lines  representing  edges  in  Fig.  2  are  fore- 
shortened?    Fig  3?     Fig.  4? 

4.  There  are  six  conspicuous  lines  in  Pig.  5  that  are  fore- 
shortened in  both  the  plan  and  the  elevation.    (1)    Which 
ones  are  they?     (2)     Were  it  necessary  for  the   drafts- 
man to  represent  them  at  their  full  length,  what  would 
be  the  only  way  to  do  it? 

5.  Why  is  the  right  hand  side  of  the  doorway  in  the  eleva- 
tion of  Fig.  5  represented  by  two  lines  and  the  left  by 
but  one? 

6.  Is  the  cros.s  in  the  church  step  buttress  cut  in  or  raised? 

7.  What  does  the  freehand  cross  hatching  at  the  bottom  of 
the  church  step  elevation  represent?     See   Plate   III. 

8.  What  do  you  interpret  the  dotted  lines  at  the  bottom  of 
the  church  steps  to  represent? 

8.  If  the  risers  to  these  steps  are  6  inches  high,  how  high 
is  the  porch  floor  they  lead  to?  A  riser  is  the  vertical 
member  of  an  individual  stair  step. 

10.  If  the  stair  treads  are  to  be  built   12  inches  wide,  how 
far  should  the  walk  layer  stop  his  walk  from  the  porch? 

11.  Is  the  eye  of  the  forging  Figs.  9  and  10  made  of  round  or 
square  stock? 


12.  What  information  do  we  have  given  as  to  whether  the  rod 
part  of  the  forging  is  round  or  square? 

13.  Why  are  the  center  lines  drawn  thru  the  drill  holes  in 
Fig.   10? 

14.  Draw  three  views  of  some  triangular  object  as  a  drafts- 
man's scale,  wood  cutter's  wedge,  etc. 

15.  Draw  the  angle  block  in  Plate  II,  Fig.  4B,  so  placed  that 
it  is  at  an  angle  with  the  vertical  plane  as  are  the  blocks 
in  Figs.  2  and  3  of  Plate  IV.   Increase  the  size  to  a  larger 
scale  for  convenience  and  accuracy  and  so  that  the  draw- 
ing conveniently  fills  a  sheet  of  sketch  paper.    Begin  by 
drawing  the  top  view  or  horizontal  projection  but  turn  it 
at  an  angle  with  the  vertical  plane  just  as  the  top  views  of 
Figs.  2  and  3  are.    Then  project  lines  down  to  locate  cor- 
responding parts  on  the  vertical  projection.    Use  section 
ruled  paper  as  that  is  the  easiest  to  work  with.     You  can 
use  the  diago'nal  of  the  squares  as  the  angle  at  which  to 
turn  your  top  view. 

16.  Draw  three  views  of  a  carpenter's  saw  horse.     Let  each 
square  on  your  paper  represent  an  inch.     Make  the  upper 
part  2  x  4  x  36  inches,  the  legs  of  1  x  4's  and  place  them 
3  inches  from  each  end  of  the  2x4.     Make  the  horse  26" 
high.     Place  the  bottoms  of  each  pair  of  feet   14  inches 
apart.     Put  in  necessary  dimensions. 

17.  Copy  the  plan  and  elevation  of  the  Building  in  Plate  IV, 
Fig.    5,   increasing   their   size   to   about   four   times   that 
shown.     Place   so.  that   the   proportionate   space  between 
the  views  is  about  twice  that  shown.     Draw  an  auxiliary 
view  of  the  front  of  the  porch  just  as  the  auxiliary  view 
of  the  Church  Steps  was  drawn  on  Plate  IV. 


VI.     SCALE  DRAWING,  DIMENSIONS 


It  is  often  found  impractical  to  make  a  drawing 
the  full  size  of  the  object  it  represents.  It  is  evident 
that  it  would  be  impossible  to  make  the  drawings  of  a 
building  and  many  other  objects  full  size,  so  draftsmen 
make  the  drawings  of  convenient  sizes  without  much 
regard  to  the  size  of  the  object  itself.  However,  there 
is  nothing  haphazard  about  the  proportions  between 
the  drawing  and  the  object  itself.  That  is  always  care- 
fully decided  upon  before  a  line  of  the  object  is  drawn. 
Small  objects  are  usually  drawn  %,  1/2,  or  /4  tne  size 
of  the  object  itself.  With  large  objects  such  as  build- 
ings an  inch  or  part  of  an  inch  represents  a  foot  on 
the  object  itself.  Thus,  if  a  scale  of  one  inch  to  a  foot 
were  used  an  object  24  ft.  long  would  be  represented 
as  but  24  in.  long  on  the  drawing.  If  a  scale  of  *4  i°-  to 
the  ft.  were  used  the  24  ft.  object  would  be  shown  by 
a  drawing  but  6  in.  long. 

The  following  are  the  more  commonly  used  scales 
with  their  proper  names. 
Scales.  Names. 

12  in.rrl  ft. .full  size  or  scale 

6  in.=l  ft..half  size  or  scale 

3  in.=l  ft. .fourth  or  quarter  size  or  scale 
\y2  in.=l  ft..eighth  size  or  scale 

1  in.=  l  ft.. one  inch  scale 

34  in.=  l  ft. .three-fourths  or  three-quarter  inch  scale 
l/2  in.=l  ft..half  inch  scale 


y&  in.=  l  ft..three-eighth  inch  scale 

J4  in.=l  ft. .one-fourth  or  quarter  inch  scale 
3/16  in.=  l  ft.three-sixteenth  inch  scale 

%  in.=  l  ft..eighth  inch  scale 

Care  should  be  taken  not  to  call  interchangeable 
the  names  of  such  scales  as  half  scale  and  half  inch 
scale.  One  represents  6  in.  as  equal  to  a  foot  and  the 
other  y2  inch  as  equal  to  a  foot. 

Drawings  drawn  to  scale  should  always  be  accom- 
panied by  a  note  stating  the  scale  of  the  drawing. 
This  is  usually  placed  as  part  of  or  accompanying  the 
title.  Note  the  statements  of  the  scale  of  the  various 
drawings  on  Plate  V.  These  statements  of  the  scales 
of  the  drawings  are  often  of  aid  to  the  workman  when 
he  finds  it  necessary  to  scale  a  drawing  for  a  dimen- 
sion. They  are  also  an  aid  in  forming  a  proper  mental 
image  of  the  actual  size  of  the  object. 

A  properly  made  drawing  should  ordinarily  not 
require  any  scaling  on  the  part  of  the  workman.  All 
dimensions  necessary  for  the  workman  should  be  on 
the  drawing  and  if  they  are  on  the  drawings  they 
should  be  depended  upon  and  not  any  scaling  on  the 
part  of  the  workman.  This  is  for  two  reasons.  First, 
blueprints  are  thoroughly  washed  during  the  process 
of  printing  and  while  wet  are  likely  to  be  more  or  less 
stretched  out  of  their  proper  size.  Second,  draftsmen 
are  not  as  particular  about  the  accuracy  of  their  draw- 


27 


BLUE  PRINT  READING 


ings  as  they  are  about  the  accuracy  of  the  dimensions. 
They  expect  the  workman  to  use  the  dimensions  that 
they  give.  If  the  draftsman  while  making  a  drawing 
discovers  that  he  has  drawn  part  of  his  drawing  wrong 
or  out  of  scale,  he  very  frequently  puts  in  the  proper 
dimensions  and  leaves  the  drawing  unchanged.  If  a 
change  of  size  should  later  be  considered  desirable,  it 
is  quite  customary  to  change  the  dimensions  without 
changing  the  drawings.  This  is  entirely  satisfactory  if 
the  workman  will  depend  upon  the  draftsman's  dimen- 
sions and  not  upon  some  of  his  own  which  he  has  ar- 
rived at  by  scaling.  Where  a  change  of  this  nature  is 
to  be  made  it  is  good  policy  on  the  draftsman's  part 
to  simply  cross  out  the  old  dimensions  and  write  in 
the  new  above  as  has  been  done  in  Fig.  1,  Plate  V. 
The  draftsman  probably  discovered  that  if  the  object 
were  made  with  the  drill  hole  located  as  drawn  there 
might  be  interference  between  the  web  connection,  be- 
tween the  eye  and  the  plate,  and  the  nut  of  the  bolt  to 
be  used  in  the  drill  hole.  As  a  change  of  the  drawing 
involved  considerable  erasing  he  simply  made  the 
necessary  corrections  by  a  change  in  the  dimensions 
and  if  the  workman  depends  upon  these  dimensions, 
instead  of  scaling,  the  Anchor  Plate  will  be  made  ex- 
actly as  the  draftsman  intended  it  should  be. 

This  drawing  illustrates,  however,  a  good  example 
of  a  very  proper  place  for  scaling,  as  the  draftsman 


has  omitted  a  dimension  for  the  hole  in  the  eye.  The 
only  way  for  the  workman  to  determine  this  is  to  scale 
the  drawing. 

Where  an  unusual  scale  is  used  or  one  not  readily 
read  from  an  ordinary  rule,  the  statement  of  the  scale 
is  usually  accompanied  by  a  line  divided  into  divisions 
in  accordance  with  the  scale.  This  is  illustrated  by  the 
Lot  Plan,  Fig.  2  where  a  scale  of  one-half  inch  equals 
50  ft.  is  used  on  the  drawing.  As  few  people  would  have 
a  rule  having  100  divisions  or  multiples  of  50  on  it  the 
draftsman  has  divided  a  one-half  inch  line  into  divi- 
sions convenient  for  scaling  of  the  drawing.  The  reader 
should  use  a  pair  of  dividers  in  taking  off  dimensions 
if  he  has  them.  If  he  has  not  he  can  use  a  strip  of 
paper  marking  off  distances  on  the  edge  with  a  sharp 
pencil  point. 

Fig.  2  illustrates  a  method  of  marking  distances  or 
dimensions  without  the  use  of  dimension  lines.  The 
dimension  is  simply  written  on  the  line  which  is  the 
length  stated  by  the  figures.  Thus  the  dimensions  75 
ft.  and  150  ft.  indicate  that  the  boundary  lines  on 
which  these  lines  are  written  are  of  these  lengths. 
This  method  of  dimensioning  is  used  a  good  deal  on 
map  drawings  and  occasionally  on  very  simple  work- 
ing drawings.  It  is  not  a  very  satisfactory  method  as 
dimensions  so  written  can  often  be  misinterpreted. 
Thus,  the  reader  might  interpret  the  150  ft.  dimensions 


ftouoh 


LOT-PLAN— Scale  l-ioorr. 
I 


ANCHOR    PL. ATE. 
CAST  Inon  - 


SECTION  THRU 

WINDOW   5IUL. 

Scale 

£JLg 


.f.,      PV  J         I  ,"•,— 

>v6T 

- 


It  M  ---  »*— 


CRANK    WHE.CL..C.I.    Fourth  Sc.t* 


1-0" 


Plate  V 


30 


BLUE  PRINT  READING 


to  be  150  ft.  to  the  fence  line,  walk  line,  curb  line  or 
even  the  street  center. 

The  method  of  dimensioning  used  in  Fig.  1  is  the 
method  in  most  general  use  and  is  by  far  the  most  ac- 
curate. The  numerals  indicate  the  dimensions  in  feet 
or  inches  or  feet  and  inches  from  end  to  end  of  the  di- 
mension line  on  which  the  numerals  are  written.  Note 
that  ends  of  dimension  lines  are  terminated  by  arrows 
and  dimensions  always  read  from  Tip  to  Tip  of  ar- 
rows. The  most  common  error  in  reading  dimensions 
is  in  noting  the  reading  of  the  numerals  but  not  noting 
carefully  where  the  Tips  of  the  arrows  terminate.  A 
careless  glance  at  the  dimensions  of  Fig.  1,  might  lead 
one  to  read  over  all  length  of  the  Anchor  Plate  as  be- 
ing 75/2"  while  a  careful  noting  of  the  tips  of  the  ar- 
rows show  that  it  is  7y2"  from  one  end  to  the  center  of 
the  eye  near  the  other  end. 

The  marks  "  over  the  numeral  as  with  the  dimen- 
sions in  Fig.  1  indicate  inches,  while  '  indicates  feet. 
The  abbreviation  "ft."  is  frequently  used  also  to  indi- 
cate feet  as  is  done  in  Fig.  2.  Where  feet  and  inches 
are  used  together  a  dash  should  separate  them.  In 
dimensions  given  in  inches  only,  the  abbreviation 
marks  are  often  omitted,  but  a  careful  draftsman 
would  never  do  this  on  an  object  where  there  might 
be  any  doubt  as  to  whether  inches  or  feet  were  in- 
tended. It  can  be  readily  understood  that  any  drafts- 


man might  omit  these  comparatively  inconspicuous 
marks  on  a  particular  dimension.  Do  not  hastily  read 
this  to  mean  inches  unless  he  has  left  the  marks  off 
of  the  entire  drawing.  If  the  dimension  numeral  is  a 
mixed  number  as  5l/2  you  can  be  quite  sure  it  is  in- 
tended as  5%  inches  as  a  careful  draftsman  never  uses 
the  dimensions  5l/2  ft.  He  would  use  5  ft.  6  in.  (5'-6".) 

The  mark  °  over  a  numeral  means  degrees,  thus, 
45°.  This  means  that  the  two  lines  or  surfaces  indi- 
cated by  the  two  arrows  leading  from  the  numerals  so 
marked  are  to  be  constructed  at  an  angle  45°  with  one 
another.  In  Fig.  3  are  two  examples  of  where  surfaces 
are  indicated  to  be  at  definite  angles  to  one  another — 
one  60°  and  the  other  45°. 

In  machine  drawings  it  is  often  necessary  to  indi- 
cate to  some  degree  how  nearly  accurate  a  dimension 
is  to  be  adhered  to.  It  is  evident  that  for  the  pur- 
poses of  a  brick  mason  dimensions  to  the  size  of  the 
nearest  multiple  of  the  width  of  a  brick  is  all  that  he 
needs  ordinarily,  but  the  machinist  who  is  making  a 
gasoline  engine  piston  head  to  fit  a  ground  cylinder 
must  do  his  measuring  in  thousandths  of  an  inch,  and 
the  draftsman  must  have  some  way  of  indicating  to 
what  degree  of  accuracy  the  dimensions  he  gives  are 
to  be  adhered  to.  This  is  done  by  using  decimal  frac- 
tions. To  illustrate,  if  a  dimension  reads  4.5"  it  would 
indicate  that  the  range  of  permissible  variation  was 


SCALE  DRAWING  DIMENSIONS 


31 


between  4.4"  and  4.6".  If  the  draftsman  wishes  the 
dimensions  to  be  more  rigidly  adhered  to,  he  states  it 
4.50"  which  would  then  allow  but  a  variation  between 
4.49"  and  4.51".  Cf  course  the  same  system  of  obtain- 
ing greater  accuracy  would  apply  if  the  dimensions 
were  stated  4.5000". 

Another  way  of  stating  the  permissible  variation — 
tolerance,  is  the  technical  teim — is  by  stating  the  di- 
mension thus, —  4.4",  4.49",  or  if  a  greater  range  of 

4.6"   4.51" 

tolerance  is  wanted  4.45" 
4.55" 

The  following  examples  will  illustrate  proper  ways 
of  stating  dimensions. 

18"     Eighteen  inches. 

18       Eighteen  inches. 

l'-6"    One  foot  six  inches. 
1  ft.  6"    One  foot  six  inches. 

5'-0"  Five  feet. 
5  ft.-O"  Five  feet. 
S'-iy^"  Five  feet,  one  and  three-fourths  inches. 

5.25     Five  and  one  quarter  inches  with  a  tolerance 
of  2   100  inches. 

5.20     Five  and  one  quarter  inches  with  a  tolerance 

5.30          range  of  20  '100  cf  an  inch. 
15°   Angle  of  fifteen  degrees. 

A  simple  way  of  dimensioning  frequently  used  in 

3 


architectural  work  is  shown  in  Fig.  4.  The  size  of  the 
pieces  are  simply  written  in  on  the  drawing  of  the 
pieces.  It  is  customary  to  use  the  approximate  sizes 
only.  Thus  the  2x4  in  Fig.  4  would  in  reality  be 
iys"x3S/8".  This  method  is  also  used  in  indicating  the 
approximate  size  of  rooms  on  floor  plans.  The  inch 
r,nd  foot  marks  are  ordinarily  omitted  as  it  is  usually 
clear  which  is  intended.  It  is  seldom  used  in  machine 
drawing. 

Where  space  is  too  crowded  to  show  dimension 
lines  by  the  regular  arrangement  of  arrows  the  ar- 
rangements shown  in  Fig.  5,  are  used.  The  arrows 
are  reversed  in  position  but  the  dimension  is  from  tip 
to  tip  of  arrows  just  as  in  the  normal  arrangement. 
This  arrangement  has  been  used  in  one  or  two  dimen- 
sions in  Figs.  1,  3,  5,  6  and  7. 

It  will  be  noted  that  all  dimensions  read  from  either 
the  bottom  or  right  hand  side  of  the  drawing.  A  care- 
ful draftsman  never  makes  exceptions  to  this  arrange- 
ment. Note  that  dimension  lines  are  shown  in  differ- 
ent ways  in  the  various  drawings  on  this  sheet.  A 
draftsman  usually  adopts  a  certain  kind  of  line  and  al- 
ways uses  it,  but  this  plate  illustrates  the  various  ways 
in  common  use.  The  arrangement  of  a  fine  solid  line 
broken  in  the  center  for  the  numerals  is  undoubtedly 
the  most  generally  used  and  probably,  all  things  con- 
sidered the  best.  If  the  lines  are  long  many  draftsmen 


32 


BLUE  PRINT  READING 


break  the  line  in  several  places  as  is  shown  in  Figs. 
6,  7  and  8. 

Figs.  7  and  8  show  variations  used  by  some  drafts- 
men. In  spite  of  this  apparent  lack  of  uniformity  there 
is  little  likelihood  of  the  reader  mistaking  a  dimension 
line  for  some  other  kind  of  line,  if  he  keeps  in  mind 
that  dimension  lines  always  have  arrow  heads  at  either 
end  and  a  numeral  is  placed  at  the  center. 

Where  arcs  are  to  be  dimensioned  the  radius  di- 
mension is  given  with  one  arrow  on  the  arc  end  of  the 
dimension  line  and  a  small  freehand  circle  at  the  center 
end.  A  few  draftsmen  use  a  small  cross  at  the  center 
end.  Many  draftsmen  put  neither  a  cross  nor  a  circle 
at  the  center  as  these  add  little  to  the  clearness  of  the 
drawing.  The  numerals  of  radii  dimensions  are  usually 
accompanied  by  abbreviations  of  the  word  radius — R., 
Rd.,  Rad.,  r.,  rd.,  rad.  Note  examples  of  radius  di- 
mension in  Figs.  1,  6,  and  7. 

Diameter  dimensions  are  frequently  accompanied 
by  abbreviations  for  the  word  diameter — D.,  Dia., 
Diam.,  dia.,  diam.  Note  diameter  dimensions  in  Fig.  7. 

Let  us  take  a  drawing  and  see  how  much  informa- 
tion we  can  get  from  it.  Fig.  3  looks  a  little  compli- 
cated so  we  will  study  that.  First  let  us  note  the  name 
— Tool  Post  Rest.  If  we  are  familiar  with  a  machine 
lathe  the  name  tells  us  a  whole  lot.  The  scale  (one- 
fourth)  gives  us  an  idea  of  its  size.  We  note  its  three 


projections  or  views  and  their  relation  to  one  another. 
By  their  relations  to  one  another  we  realize  that  the 
largest  of  the  three  is  the  top  view  or  horizontal  pro- 
jection and  the  others  are  side  and  front  projections. 
Looking  at  the  overall  dimensions  we  find  that  it  is 
5S/8"  long,  3y2"  wide  and  iy8"  high.  The  first  two  of 
these  dimensions  are  given  on  the  top  view,  the  height 
is  given  on  the  front  view.  It  could  also  be  found  by 
adding  the  \ys"  and  J4"  dimensions  on  the  end  (or 
side)  view.  It  is  also  discovered  to  be  approximately 
a  rectangular  solid  in  shape. 

Probably  the  most  conspicuous  variation  of  the  ob- 
ject from  a  rectangular  solid  is  found  probably  first  in 
the  end  view  where  a  dovetail  groove  is  shown  on  the 
bottom.  Dotted  lines  on  the  other  views,  one  on  the 
front  view  and  four  on  the  top  view  show  that  this 
groove  goes  the  entire  length  of  the  object.  The  di- 
mensions show  that  this  dovetail  is  y2"  deep  and  15/g" 
wide.  As  these  dimensions  are  stated  decimally — .50" 
and  1.625",  these  dimensions  are  evidently  to  be  very 
closely  adhered  to  by  the  workman.  The  15  '16"  di- 
mensions on  either  side  of  the  1.625"  dimensions  shows 
that  this  dovetail  groove  is  placed  exactly  in  the  center 
of  the  object.  The  60°  angle  dimension  at  the  side  of 
the  dovetail  groove  shows  the  angle  which  the  side  of 
the  groove  makes  with  the  bottom  of  the  object. 

The  conspicuous  mass  of  dotted  lines  in  the  top  and 


SCALE  DRAWING  DIMENSIONS 


33 


front  views  must  represent  a  threaded  hole.  This  sur-. 
mise  is  proved  by  the  concentric  circle  and  near  circle 
on  the  other  view.  The  circle  represents  the  inner 
edge  or  top  of  the  threads,  the  near  circle  the  bottom 
of  the  threads.  The  note,  "54  U.  S.  S.  threads,"  shows 
the  diameter  of  the  hole  and  that  the  threads  are  ordi- 
nary United  States  Standard  threads.  The  horizontal 
(kft  to  right)  center  line  passing  through  the  threaded 
hole  shows  that  it  is  in  the  center  of  the  piece. 

The  most  conspicuous  thing  which  the  front  view 
brings  out  is  the  inverted  "T"  groove  near  the  right 
hand  end.  Glancing  back  to  the  top  view  we  see  that 
this  groove  is  shown  on  this  view  by  two  solid  lines 
and  two  hidden  edge  lines.  These  establish  the  fact 
that  this  "T"  groove  runs  entirely  across  the  Rest. 
Inspection  of  the  end  view  fails  to  show  any  trace  of 
this  groove  though  two  hidden  edge  lines  should  be 
there.  The  draftsman  has  evidently  decided  that  the 
groove  was  fully  shown  by  the  other  views  and  has 
made  use  of  his  privilege  of  omitting  anything  on  a 
drawing  which  does  not  give  increased  information. 
The  dimensions  show  that  this  groove  is  5/g"  wide  at 
the  top  and  1%"  wide  at  the  bottom,  the  narrow  part 
7/16"  deep  and  the  wide  part  5/16".  The  dimensions 
also  definitely  locate  the  position  of  the  groove  as 
being  %"  from  the  right  hand  end  of  the  Rest. 

While    getting    this    information    the    reader    has 


doubtlessly  discovered  that  the  top  is  not  flat  as  he 
may  have  supposed  it  to  be  at  first  glance.  He  has 
probably  discovered  that  the  right  hand  end  of  the  top 
is  chamfered  off  at  the  corner.  The  dimensions  show 
that  this  chamfer  (or  bevel)  is  y$"  wide  and  at  an 
angle  of  45°  with  the  end.  The  left  end  is  more  modi- 
fied still.  The  end  view  shows  that  a  curved  ridge 
extends  along  the  top  directly  over  the  tapped  $/%" 
hole.  This  is  evidently  intended  to  thicken  the  metal 
along  this  hole  without  adding  to  the  entire  block. 
That  this  ridge  does  not  extend  entirely  across  is 
shown  in  the  top  and  front  views.  The  front  view 
shows  this  by  a  solid  line  representing  the  flat  surface 
at  the  side  of  the  ridge,  showing  that  it  dies  away  in 
a  rise  of  the  surface  3*4"  from  the  left  end.  The  top 
view  shows  this  ending  of  the  ridge  by  a  curved  line 
of  intersection. 

If  this  ridge  had  made  a  distinct  line  of  intersection 
with  the  top  instead  of  flowing  into  it  with  a  flowing 
curve,  as  shown  on  the  end  view,  the  sides  of  the  ridge 
would  have  made  lines  on  the  top  view. 

This  discussion  of  what  is  shown  in  the  drawing  of 
Fig.  3  certainly  shows  that  the  great  universal  lan- 
guage of  mechanical  drawing,  is  an  exact  expressive 
compact  language,  much  better  suited  to  the  purpose 
for  which  it  is  used  than  any  other  language  could  hope 
to  be. 


34 


BLUE  PRINT  READING 
QUESTIONS    AND    PROBLEMS. 


1.  Assuming  that  the  house  in  Plate  IV  is  20  ft.  by  24  ft., 
what  scale  is  it  drawn  at? 

2.  What  are  the  over  all  dimensions  of  the  house  in  Fig.  2, 
Plate  V? 

3.  What  direction  does  the  house  front? 

4.  Is  the  House  Plan,  Fig.  8,  one-sixteenth  scale  or  one-six- 
teenth inch  scale? 

5.  What  are  the  overall  dimensions  of  the  Anchor  Plate? 

6.  In  dimensioning  radii  in  the  Angle  Plate,  which  has  the 
draftsman  made  use  of,  for  the  center  of  his  dimension 
line,  the  small  freehand  circle  or  the  cross? 

7.  What  has  he  used  as  his  abbreviation  for  Radius? 

8.  Where  might  he  have  used  the  abbreviation  for  Diameter? 

9.  What  are  the  dimensions  of  the  drill  holes  in  the  Anchor 
Plate?    The  Eye  Hole? 

10.  What  is  the  short  width  of  the  dovetail  groove  in  the 
Tool    Post   Rest?     The    depth?     What   angles   are   the 
side  at? 

11.  What  is  the  approximate  depth  of  the  tapped  hole? 

12.  How  many  pieces  of  two  inch  lumber  are  shown  in  cross 
section  in  Fig.  4?     One  inch? 

13.  What  do  you  interpret  the  sections  on  Fig.  4  shown  as 
fine  scattered  dots  to  represent? 

14.  How  many  examples  of  the  Fig.  5   (A)   style  of  dimen- 
sioning do  you  find  on  this  sheet?     (B)?     (C)? 

15.  What  is  the  diameter  of  the  Crank  Wheel?    Width  of  the 
wheel  face?     Diameter  of  the  hub? 


16.  The  draftsman  has  neglected  to  put  in  what  is  from  the 
standpoint  of  his  entire  machine  probably  the  most  im- 
portant dimensions  on  the  drawing.   Where  is  it?    What 
should  the  length  be  as  you  scale  it? 

17.  What  are  the  diameters  of  the  holes  through  the  wheel? 

18.  How  can  you  tell  center   lines  from  dimension  lines   in 
Fig.  If 

19.  What   is    the    diameter    of   the    large    hole    through   the 
Spindle  Sleeve? 

20.  Why  are  two  diameters  given  for  the  three  holes  through 
the  flanges  of  the  Spindle  Sleeve? 

21.  How  far  are  the  centers  of  those  holes  from  the  center 
of  the  Sleeve? 

22.  How  many  square  feet  of  lumber  will  it  take  to  cover 
the  porch  of  the  house,  Fig.  8,  allowing  l/$  for  waste? 

23.  Allowing  walls  to  be  6  inches  thick,  what  is  the  actual 
inside  size  of  the  Bed  Room? 

24.  Which   is   the    larger   on   the    inside,   the    Closet    or   the 
Pantry? 

25.  Draw  a  full  size  drawing  of  an  ink  bottle  and  give  the 
principal  dimensions.     Do  not  neglect  to   put   in  center 
lines. 

26.  Draw  a  water  tumbler  or  tin  cup  half  scale  and  dimension. 

27.  Draw  a  box  similar  to  the  one   on   Plate   I   stating  the 
scale   and   dimensioning    so   that   the   full    dimensions    of 
every  piece  in  the  box  are  fully  given.  Draw  3  projections. 


VII.     BREAKS,  REPRESENTING  DRAWINGS  AS  BROKEN 


Draftsmen  very  frequently  draw  objects  repre- 
sented as  tho  they  had  gone  thru  some  serious  acci- 
dent— they  represent  the  objects  as  being  broken. 
Sometimes  an  end  is  broken  off,  often  the  part  broken, 
out  in  the  center.  The  draftsman  does  not  want  the 
workman  to  make  the  object  broken  as  represented, 
but  the  break  is  put  in  the  drawing  simply  as  a  con- 
venience to  the  draftsman.  The  most  frequent  use  of 
the  break  is  probably  to  save  drawing  space.  The 
break  in  the  Drafting  Tee-Square  in  Plate  VI  was 
for  that  purpose.  By  breaking  a  piece  out  of  the  blade 
of  the  Tee-Square  the  draftsman  was  able  to  shorten 
his  drawing  by  over  half.  Scaling  will  show  that  he 
had  represented  the  36"  blade  as  only  about  11",  tho 
the  dimension  reads  36".  Of  course  the  workman  is 
to  make  it  a  perfectly  good  Tee-Square  and  full  36" 
long.  It  is  evident  that  dimension  lines  and  not  scal- 
ing must  be  relied  upon  in  reading  a  dimension  extend- 
ing across  a  break. 

The  Connecting  Rod  End  is  a  good  illustration  of 
another  use  of  a  break — to  show  only  a  part  of  an 
object.  Evidently  the  draftsman  did  not  consider  it 
necessary  to  represent  the  entire  Connecting  Rod  so 
he  broke  off  the  desired  part.  It  is  evident  that  the 
arrangement  of  his  projections  also  forced  him  to  re- 
sort to  breaks  to  prevent  his  projections  from  conflict- 


ing. This  same  necessity  for  breaking  the  drawing 
occurred  in  Fig.  10  of  Plate  IV. 

Note  in  the  Connecting  Rod  End  the  use  of  cross 
hatch  (close  parallel)  lines  to  indicate  the  broken  sur- 
face. Note  also  the  peculiar  shape  of  the  break  itself. 
This  way  of  representing  a  broken  cylindrical  or  ellip- 
tical part  is  almost  universal.  Note  the  way  of  repre- 
senting the  breaks  in  the  Broken  Cylinder  and  the 
Broken  Pipe. 

In  small  parts  the  broken  surface  is  often  repre- 
sented in  solid  black  (white  on  blueprint,  of  course). 
This  is  illustrated  by  the  Broken  T-iron,  and  the 
Clamp  Lever. 

Wood  is  usually  represented  by  a  more  ragged 
break  line  than  iron  as  shown  in  the  drawing  Broken 
Wood,  and  Pier  and  Framing,  tho  this  is  not  always 
the  case. 

The  left  hand  break  in  the  Lathe  Tail  Stock  Spindle 
Sleeve  and  the  break  in  the  Collar  and  Button  Box, 
represent  a  use  of  the  break  for  the  purpose  of  showing 
parts  in  the  interior  of  the  object.  In  the  Collar  and 
Button  Box  the  draftsman  has  broken  a  hole  in  the 
side  of  the  outer  part  of  the  box  so  that  the  button  box 
part  shows  through  the  break.  In  the  case  of  the 
Spindle,  by  breaking  away  the  end  the  draftsman  has 
been  able  to  represent  a  section  of  the  brass  threaded 


35 


BLUE  PRINT  READING 


collar  much  clearer  than  would  have  been  possible  by 
hidden  edge  lines. 

Often  a  part  of  an  object  is  shown  without  a  dis- 
tinct breaking  off  line  being  shown,  as  illustrated  in 
the  Porch  Corner.  Here  the  lines  representing  the 
porch  rails  are  simply  stopped  after  they  have  been 
drawn  as  long  as  is  necessary  for  the  purposes  of  the 
draftsman,  no  distinct  breaking  off  line  being  shown. 
This  is  very  frequently  used  by  architectural  drafts- 
men, but  not  so  much  by  machine  draftsmen.  Note 
that  even  the  dimension  line  is  broken  off.  This  is  not 
often  done,  however,  as  nothing  is  definite  as  to  what 
the  other  end  of  the  object  is  like. 

The  Porch  Column  shows  a  way  of  representing  a 
breakline  used  very  largely  by  architects.  It  is  little 
used  by  machine  draftsmen.  The  break  line  is  drawn 
partly  with  a  straight  edge  and  partly  free  hand. 

QUESTIONS   AND    PROBLEMS. 

1.  What  changes  would  be  necessary  in  the  drawing  of  the 
Drafting  Tee-Square  to  represent  a  30  inch  Tee-Square? 

2.  What    dimensions    are    omitted   in   the    Tee-Square    that 
might  be  put  in  if  the  draftsman  were  unwilling  to  trust 
to  the  judgment  of  the  workman? 

3.  What  projections  (or  views)  has  the  draftsmen  made  use 
of  in  the  Connecting  Rod  End? 

4.  If  we  consider  bricks  to  be  2  inches  x  4  inches  x  8  inches, 
what  is  the  width  and  thickness  of  the  pier  in  the  draw- 
ing Pier  and  Framing? 


5.  What  kind  of  drawing  is  the  Pier  and  Framing?     Refer 
to  chapter  I  if  necessary. 

6.  What  do  the  hidden  edge  lines  in  the  top  view  of  the 
Collar  and  Button  Box  represent? 

7.  Is  the  Button  Box  part  round  or  square  and  how  do  you 
know? 

8.  Why  are  no  dimensions  given  for  the  taper  in  the  Lathe 
Tail  Stock  Spindle? 

9.  What   besides   the   end  view   shows  that   the    Spindle   is 
both  round  and  hollow? 

10.  What  are  the  dimensions  of  the  small  brass  piece  in  the 
Spindle? 

11.  How  long  over  all  is  the  Clamp  Lever? 

12.  What  besides  the  dotted  lines  showing  threads  shows  that 
the  hole  in  the  Clamp  Lever  is  threaded? 

13.  Since  no  end  view  is  shown,  how  do  you  know  that  the 
tapered  bar  to  the  Clamp  Lever  is  round  and  not  square? 
There  are  two  distinct  things  that  show  it? 

14.  Does  the  keyway  in  the  Lathe  Tail  Stock  Spindle  extend 
the  entire  length  of  the  spindle? 

15.  Add  the  smaller  vertical  dimensions  on  the  Porch  Column 
to  see  if  they  agree  with  the  stated  over  all  height  of  8 
feet. 

16.  How  many  linear  feet  of  corner  boards  would  be  needed? 

17.  Allowing  3  inches  for  lap  and  waste  on  each  piece,  how 
many  linear  feet  of  lumber  would  be  needed  for  the  panels 
of  the  Porch  Column? 

18.  How  many  linear  feet  of  2  inches  x  4  inches  would  be 
needed  for  the  hand  and  bottom  rails  of  the  Porch  Corner? 

19.  How  many  linear  feet  of  1  inch  square  lumber  would  be 
required   for   balusters,   allowing    1    inch    waste   on   each 
baluster? 


-36" 


eti — a 

T*         "* 


•v*  CONNECTING   ROD  ENC. 

DRAFTING    TEE- SQUARE 
Scale   /r'ff^O" 


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COL.LAR  AND  BUTTON  BOX 
sale  lr"-=l'-0" 


WOOD 


\THEi    TAIL.   STOCK  5PINDL.E. 
TCEL.  -  Scale   6"-l-O" 


•  PIER  ANO  FRAMING  - 


CL.AMP    LEVE.R  - STCCL. 
Scale   6*l'-O" 


Plate  VI 


37 


VIII. 

Draftsmen  frequently  represent  parts  of  objects  as 
they  would  appear  were  the  object  cut  in  two.  Draw- 
ings which  represent  this  cut  surface  are  known  as  sec- 
tions. Such  a  drawing  was  illustrated  in  Fig.  8, 
Plate  III. 

Sections  are  usually  represented  with  closely  drawn 
parallel  lines  (cross  hatching)  covering  the  cut  sur- 
face. These  lines  can  be  considered  as  representing 
scratches  left  by  the  saw  in  cutting  the  object.  Whe- 
ther or  not  this  is  what  they  are  supposed  to  represent, 
it  is  a  simple  interpretation  that  if  kept  in  mind  helps 
one  to  understand  the  meaning  of  a  cross  section. 

Sections  are  usually  made  along  center  lines  as  was 
done  in  the  case  of  the  Spool  Fig.  8,  Plate  III,  but  this 
is  not  always  the  case.  Where  such  is  not  the  case 
lines  similar  to  center  lines  are  drawn  on  the  main 
drawing  to  locate  where  the  section  is  to  be  made. 
This  is  illustrated  in  the  drawing  Wrench,  Plate  VII. 
The  small  circular  drawing  "Section  AA"  is  a  drawing 
of  the  end  of  the  handle  of  the  Wrench  were  it  sawed 
off  on  the  dot-and-dash  line  crossing  the  two 
views  of  the  main  drawing  and  marked  with  a  capital 


SECTIONS 

"A"  at  either  end.    The  other  sections  "BB",  "CC"  and 
"DD"  represent  other  sections  on  similar  lines. 

Sections  often  represent  more  than  just  the  surface 
cut  in  that  they  may  represent  a  part  of  the  object 
which  would  appear  in  the  background  after  the  sec- 
tion is  cut  off.  This  is  illustrated  by  the  section  "DD" 
of  the  Wrench,  where  two  horizontal  lines  represent 
the  top  and  bottom  of  the  back  part  of  the  opening  for 
the  nut,  and  a  central  vertical  line  represent,  the  back 
corner  of  the  same  opening. 

Often  instead  of  drawing  small  section  views  off  to 
one  side  the  draftsman  draws  the  section  on  the  main 
drawing  itself  as  has  been  done  in  the  drawing  of  the 
"C"  clamp.  Here  the  draftsman  has  drawn  a  small 
"T"  shaped  cross  section  on  the  frame  of  the  clamg 
which  is  to  indicate  that  the  frame  at  this  point  is  the 
shape  of  the  section.  He  has  also  drawn  in  a  small 
section  on  the  wing  of  the  thumb  screw  which  shows 
the  thickness  and  shape  of  the  part  there.  These  sec- 
tions make  it  unnecessary  for  any  top  or  side  view 
being  drawn  altho  the  draftsman  has  had  to  draw 
a  small  auxiliary  view  to  show  the  shape  of  the  anvil 
of  the  clamp. 
38 


Sect.         Sact.       Sect.         Sect- 
AA  00          £C  DO 

WRENCH 


•SECTION' or 'WALL, 


SET    COLLAR 


PACKING    GL.AND 


C     CLAMR 


•POR.CH° 
-COLUMN' 


PILLOW  BLOCK  BEARING 


-22- 


SWIN6     BOARD 


IT 


•  NEWEL- 


:1 


Plate  VII 


39 


40 


BLUE  PRINT  READING 


The  Newel  also  illustrates  the  use  of  this  same  kind 
of  section.  The  section  drawn  on  the  face  of  the  Newel 
shows  that  the  central  part  is  square  and  is  framed  up 
of  four  boards.  It  also  shows  the  dimension  of  this 
part. 

The  cross  hatching  of  wood  is  usually  done  free- 
hand, as  is  done  in  this  Newel  section,  and  in  such  a 
manner  as  to  represent  the  grain  of  the  wood. 

The  sections  in  the  "C"  Clamp  and  Newel  are 
known  as  revolved  sections  as  they  represent  sections 
revolved  at  right  angles  with  the  main  part  of  the 
drawings. 

The  balusters  and  rails  on  the  Porch  Corner,  Plate 
VI,  show  further  examples  of  the  use  of  the  revolved 
section. 

Occasionally  only  a  small  part  of  a  revolved  sec- 
tion is  drawn  as  the  section  representing  and  showing 
the  thickness  of  the  Swing  Board.  Here  the  draftsman 
has  saved  himself  the  labor  and  space  required  for  a 
second  view  by  inserting  this  small  partial  or  broken 
revolved  section.  He  could  very  easily  have  represent- 
ed the  section  on  the  wing  of  the  thumb  screw  of  the 
"C"  Clamp  in  the  same  way. 

Closely  related  to  these  revolved  sections  is  the 
inserted  section  illustrated  in  the  Porch  Column. 


In  these  the  section  is  revolved  but  is  inserted  in  a 
broken  out  space.  These  are  very  handy  to  use  on  a 
tapered  part  like  the  Porch  Column  where  the  taper 
would  make  it  awkward  to  use  a  simple  revolved  sec- 
tion. 

Often  a  section  is  used  in  place  and  in  the  position 
of  the  view.  This  was  done  in  the  section  on  Plate 
III  where  a  section  of  the  Spool  was  used  for  the  side 
projection.  In  the  drawing  of  the  Packing  Gland, 
Plate  VII,  a  section  is  used  in  place  of  the  front  pro- 
jection. Where  this  kind  of  section  is  used  it  is  almost 
always  a  section  on  the  center  line  of  the  object. 

The  Set  Collar  is  another  example  of  where  a  sec- 
tion is  used  in  place  of  a  projection.  Note  that  while 
the  Set  Collar  itself  is  rendered  in  section — right  hand 
projection — the  shaft  and  set  screw  are  not  sectioned. 
This  is  in  accord  with  almost  universal  custom  among 
draftsmen — cylindrical  parts  inside  of  sectioned  parts 
are  not  rendered  in  section. 

Often  draftsmen  use  as  a  combination  a  regular 
outside  view  and  a  cross  section,  rendering  half  in 
section  and  half  as  an  ordinary  outside  view.  An  ex- 
ample of  this  arrangement  is  found  in  the  Tie  Ring 
where  the  right  hand  view  is  rendered  with  the  part 
above  the  center  line  in  section  and  the  part  below  as 


SECTIONS 


an  ordinary  projection.  This  is  a  very  satisfactory  way 
of  drawing  objects  which  are  symmetrical  with  a  cen- 
ter line.  The  section  shows  the  inside  construction 
much  clearer  than  hidden  edge  lines  could  do,  while 
the  part  not  rendered  in  section  clearly  shows  the  out- 
side of  the  object. 

The  Pillow  Block  Bearing  is  another  example  of 
half  view  half  section,  the  dividing  line  being  on  the 
vertical  center  line.  Note,  however,  that  the  section 
is  not  along  the  horizontal  (top  view)  center  line  but 
is  along  a  zigzagged  section  line  marked  "EE".  This 
is  quite  common  practice  and  enables  the  draftsman 
to  make  his  section  give  a  greater  amount  of  informa- 
tion than  he  might  otherwise.  By  zigzagging  his  sec- 
tion line  he  has  made  his  section  show  both  a  bolt  hole 
and  the  oil  hole  which  could  not  have  been  done  by  a 
straight  cut  out  section.  This  zigzagging  of  the  sec- 
tion line  is  very  handy  in  house  plans  where  it  enables 
the  architect  to  make  a  choice  of  rooms  to  show  in  his 
cross  section  views. 

The  section  line  "EE"  on  the  Pillow  Block  Bearing 
has  arrows  on  the  ends.  These  arrows  indicate  the 
direction  in  which  the  reader  is  to  consider  himself  as 
looking  when  reading  the  section  view.  These  arrows 
are  hardly  necessary  on  this  drawing  because  the  loca- 
tion of  the  section  itself  shows  the  direction  the  section 


is  to  be  considered  as  being  viewed  from.  On  house 
drawing,  where  each  view  and  section  has  to  be  on  a 
separate  sheet  of  paper,  these  arrows  are  frequently  of 
considerable  help  in  reading  a  drawing. 

The  drawing  Section  of  a  Wall  illustrates  some 
common  practices  in  making  house  sections.  Dimen- 
sion timbers  shown  in  section  are  not  cross  hatched 
by  some  draftsmen  but  they  use  a  convention  of  cross- 
ing diagonal  lines  instead,  as  is  used  in  this  drawing 
for  the  plates  and  sills.  The  siding,  sheathing,  floor- 
ing, and  other  thin  parts  are  not  cross  hatched  as  they 
are  so  thin  on  the  drawing  as  to  make  a  cross  hatching 
impractical.  Where  the  sections  are  drawn  to  a  larger 
scale  these  parts  are  usually  cross  hatched  by  careful 
draftsmen. 

Note  that  the  cross  hatching  across  the  brickwork 
shows  that  the  brickwork  is  cut  by  the  section.  This 
shows  that  the  house  rests  on  a  brick  wall  and  not  on 
brick  piers. 

Sections  are  a  very  important  part  of  many  working 
drawings  and  it  is  important  that  he  who  must  read 
drawing  should  thoroly  understand  them.  Nothing 
will  make  them  clearer  than  to  remember  that  cross 
hatch  lines  represent  scratches  made  by  the  imaginary 
saw.  He  must  also  learn  to  know  on  what  line  the 
section  is  cut. 


BLUE  PRINT  READING 
QUESTIONS    AND    PROBLEMS. 


1.  What  is  the  principal  information  to  be  gotten  from  the 
top  view  of  the  Wrench  which  is  not  sufficiently  given  by. 
the  front  view  and  the  sections? 

2.  What  are  the  over  all  dimensions  of  the  Packing  Gland? 

3.  How  many  pieces  of  metal  is  the  Packing  Gland  made  of? 

4.  What  do  the  4  concentric  circles  in  the  center  of  the  plan 
(top  view)  of  the  Pillow  Block  Bearing  represent? 

5.  Are  the  4  bolt  holes  in  the  Bearing  threaded?     The  bolt 
holes  in  the  Packing  Gland? 

6.  What  holds  the  Set  Collar  in  place  on  the  shaft? 

7.  How  many  pieces  of  boards  make  up  the  shaft  or  central 
part  of  the  Forch  .Column? 

8.  What  kind  of  joint  is  used  in  fastening  these  together, 
butt  or  miter? 

9.  How  thick  is  the  Swing  Board? 

10.  How  many  pieces  make  up  the  Tie  Ring? 

11.  A  prominent  line  has  been  omitted  on  this  drawing.   What 
is  it? 

12.  What  size  timbers  are  used  for  rafters  in  Section  of  Wall? 


13.  How  long  are  the  wall  studs? 

14.  What   information   do   we   have   as  to  the  shape   of  the 
barrel  through  which  the  screw  in  the  "C"  Clamp  goes 
which  shows  that  it  is  round  and  not  square? 

15.  Draw  a  two  view  detail  of  the  barrel  of  the  "C"  Clamp 
as  it  would  appear  were  it  square.     Break  the  barrel  off 
so  as  to  save  drawing  the  entire  clamp  frame. 

16.  Make  a  full  size  detail  drawing  of  each  piece  of  the  Tie 
Ring  using  all  necessary  views  or  sections  to  fully  show 
each  part.    Dimension  fully  each  part. 

17.  Make  a  full  sized  drawing  of  the  Packing  Gland  using 
three  views.    Make  the  front  view  a  combined  section  and 
front  view  like  the  front  view  of  the  Pillow  Block  Bear- 
ing. 

18.  Draw  the  Wrench  using   an  end  view  and   a  top  view. 
Place  a  revolved  section  in  the  handle  part  and  an  in- 
serted section  in  the  central  portion. 

19.  Draw  the  Newel  using  top  view,  front  view  and  a  sec- 
tional side  view. 


IX.     BOLTS,  SCREW  THREADS,  MACHINING  OR  FINISH 


Bolts  and  nuts  are  not  difficult  to  recognize  on  a 
drawing  but  are  easily  mistaken  as  to  kind.  Bolt  heads 
and  nuts  arc  ordinarily  either  hexagonal  qr  square. 
These  are  shown  in  Figs.  1  and  2,  Plate  VIII.  It  is 
not  difficult  to  distinguish  between  the  square  and 
hexagonal  nuts  or  bolt  heads  in  top  views  but  side 
views  are  sometimes  confusing  when  a  corner  rather 
than  flat  face  is  represented  as  being  toward  the  read- 
er, as  is  the  case  in  the  front  view  of  Fig.  1  and  the 
auxiliary  view  of  Fig.  2. 

Note  the  conventionalized  method  of  representing 
the  screw  threads  in  these  two  figures.  Note  that  these 
lines  are  not  drawn  exactly  at  right  angles  with  the 
axles  of  the  bolts  though  occasionally  they  are  so  rep- 
resented by  draftsmen,  as  in  Fig.  4.  The  advantage  of 
showing  them  with  a  slight  pitch  is  that  it  gives  the 
draftsman  a  chance  to  differentiate  between  a  right 
hand  and  a  left  hand  thread.  A  little  thought  will 
make  it  clear  that  the  nuts  on  these  two  bolts  would 
be  turned  clockwise  in  being  screwed  on  to  the  bolts. 
The  threads  are  therefore  right  hand  threads.  Note 
that  the  threads  on  the  bolt  end  shown  in  Fig.  3  are 
slanting  opposite  from  those  in  Figs.  1  and  2  so  these 
threads  are  clearly  left  hand  threads.  Where  drafts- 
men draw  these  threads  perpendicular  to  the  axis  of 
the  bolt  the  reader  can  safely  assume  that  they  repre- 


sent right  hand  threads  unless  an  accompanying  note 
specifically  indicates  otherwise. 

Figs.  4,  5,  6  and  7  indicate  other  common  screw 
thread  conventions.  Fig.  8  shows  five  holes  tapped 
with  screw  threads — A  being  shown  with  a  stud  in  it. 
Note  the  top  views  of  these  holes.  Note  that  the  dotted 
line  representing  the  bottom  of  the  screw  threads  in 
the  plan  of  A  is  differently  placed  from  that  of  B  and 
C.  This  placing  of  the  dotted  line  makes  clear  the  dif- 
ference in  top  views  between  a  stud  and  a  tapped  hole. 
In  the  top  view  of  D  the  dotted  circle  is  replaced  by  an 
arc  of  a  circle.  Though  probably  not  as  much  used  as  a 
fully  dotted  circle  it  should  be  recognized  as  meaning 
exactly  the  same  thing.  E  is  an  example  of  where 
threaded  lines  are  drawn  horizontally  and  does  not 
show  the  hand  of  the  threads. 

Note  that  the  stud  in  A  is  not  represented  as  being 
entirely  through  the  hole,  also  that  the  threads  on  the 
stud  are  right  hand  threads.  The  reader  will  note  that 
the  threads  in  the  hole  below  the  stud  are  drawn  at  a 
reverse  angle  to  those  on  the  stud.  This  does  not  indi- 
cate that  the  draftsman  has  represented  a  stud  having 
right  hand  threads  in  a  hole  tapped  with  left  hand 
threads.  If  the  reader  will  recall  that  the  front  of  the 
hole  is  represented  as  being  bioken  out  so  that  he  sees 
the  back  side  of  the  hole  where  the  angle  of  the  threads 


43 


44 


BLUE  PRINT  READING 


are  the  reverse  of  the  front  side,  it  will  be  clear  that 
these  threads  are  really  right  hand  threads.  Of  course, 
the  threads  shown  on  the  stud  are  those  on  the  front 
side.  Care  must  be  taken  in  reading  screw  threads  as 
represented  in  sections  or  breaks  to  keep  in  mind  this 
matter  or  the  reader  will  interpret  them  as  being  wrong 
hand. 

Where  screw  threads  are  shown  by  dotted  lines  as 
in  "C"  they  are  either  drawn  perpendicular  to  the  axis 
of  the  hole  or  at  the  proper  angle  for  the  side  of  the 
hole  nearest  the  reader. 

Because  it  is  so  easy  to  misinterpret  the  hand  of 
screw  threads  and  because  most  threads  are  made 
right  hand  anyway,  it  is  usually  safe  to  call  all  threads 
right  hand  unless  specifically  indicated  by  a  note  as 
otherwise  or  the  construction  obviously  demands  a  left 
hand  thread. 

In  machine  shop  work  the  filing,  turning  or  other- 
wise smoothing  up  of  rough  iron  is  known  as  Finish. 
The  note  accompanying  the  drawings  of  Figs.  1  and  2 
"Finish  all  over,"  indicates  that  these  bolts  are  to  be 
finished  on  all  surfaces.  The  small  italic  f's  drawn 
across  the  boundary  lines  of  the  rectangular  piece, 
Fig.  8,  indicate  that  these  faces  are  to  be  finished  or 
machined.  Occasionally,  draftsmen  use  the  words 


"turn,"  "plane,"  "face,"  etc.,  instead  of  the  word,  "fin- 
ish or  the  letter  /. 

Finish  is  indicated  in  Figs.  3  and  6,  Plate  V.  In 
Fig.  6  the  word  "turn."  is  used  to  show  that  the  piece 
is  to  be  turned  down  to  the  stated  size.  In  this  draw- 
ing the  draftsman  has  departed  from  the  more  usual 
custom  of  using  a  small  /  by  using  a  capital  F. 

QUES    IONS    AND    PROBLEMS. 

1.  Are  the  threads  right  or  left  hand  in  the  Connecting  Rod 
End  Plate  VI? 

2.  How  are  the  threads  of  the  Clamp  Lever,  Plate  VI,  to  be 
made,  by  chasing  or  by  tapping? 

3.  If  this  piece  were  turned  over  to  you  to  thread  would  you 
thread  it  right  or  left  hand? 

4.  Are  the  square  threads  in  the  Lathe  Tail  Stock  Spindle, 
Plate  VI,  right  or  left  hand? 

5.  What  screw  threads  do  you  find  on  Plate  VII? 

6.  Copy  Fig.  10,  Plate  IV,  at  an  enlarged  scale  and  show  the 
four  holes  in  the  end  as  being  tapped  for  threads. 

7.  Make  a  sketch  of  the  Lathe  Faceplate,  Fig.  7,  Plate  III, 
but    represent    it    in    section    and    with    the    large    hole 
properly    threaded.     Indicate    properly    on    your    sketch 
such  surfaces  as  should  be  machined. 


Tj&g  full  heads 

Countersunk  and 
chipped 

CountersunH  and  not  , 
chipped,  or  f/ottenedg 

Flattened  /' 


Flattened 


SHOP  RIVETS 


fronts/lie  Elevation  Buck  sale  Both  -.ida 


o 


> 


RIVETS 


Fr  outside  Elevation  Sack  side  Beth  sides 


SYMBOi-S 


L*  sum  us  other  tnd 


STRUCTURAL   STEEL   MEMBE.R 


l_i-      \7TTT 


X.     RIVETS— STRUCTURAL  STEEL 


Structural  steel  drafting  is  so  influenced  by  the 
character  of  the  material  drawn  that  it  will  be  well 
to  give  a  little  special  study  to  it. 

Rivets  which  are  drawn  on  ordinary  machine  draw- 
ings are  ordinarily  drawn  strictly  in  accordance  with 
the  rules  of  projections  and  anyone  familiar  with  work- 
ing drawings  can  interpret  the  kind  of  rivet  indicated 
if  he  never  saw  a  rivet.  On  structural  steel  work, 
rivets  form  such  an  important  part  of  almost  every 
drawing  that  draftsmen  have  adopted  a  very  conven- 
tionalized set  of  symbols  for  representing  rivets.  A 
chart  of  these  rivet  symbols  is  shown  on  Plate  VIII. 
It  should  be  carefully  studied. 

Note  that  this  chart  divides  rivets  into  two  classes, 
Shop  Rivets  and  Field  Rivets.  Shop  rivets  are 
such  rivets  as  are  put  in  in  building  up  the  parts 
in  the  shop  while  field  rivets  are  put  in  on  the  job. 
The  holes  are  drilled  and  if  the  drawing  calls  for  it, 
countersunk  in  the  shop  for  field  rivets.  Field  rivets 
are  always  represented  in  solid  even  in  elevation. 

Plain  rivets  button  head  on  both  ends,  are  indi- 
cated in  end  views  by  a  small  circle  the  size  of  the  rivet 


head.    If  it  is  to  represent  a  hole  for  a  field  rivet,  it  is 
drawn  the  size  of  the  rivet  shank  and  filled  in  solid. 

Countersunk  rivets  are  indicated  by  crossing  lines. 
If  the  countersunk  end  is  toward  the  reader,  the  cross- 
ing lines  are  only  shown  without  the  circle,  if  counter- 
sunk on  the  side  away  from  the  reader  the  cross  is 
within  the  circle,  if  the  rivet  is  to  be  countersunk  on 
both  ends,  the  crossing  lines  are  indicated  both  within 
and  without  the  circle. 

The  height  to  which  rivets  are  to  be  flattened  is 
indicated  on  the  end  views  by  a  single  line  across  the 
center  of  the  circle  for  those  flattened  y%"  high,  two 
parallel  lines  for  28"  high  and  three  lines  for  ys"  high. 
These  lines  conform  to  the  same  arrangement  regard- 
ing the  circle  as  those  indicating  the  countersink — 
appearing  outside  the  circle  only  for  the  end  toward 
the  reader,  inside  for  the  end  away  from  the  reader, 
both  outside  and  inside  for  both  ends. 

Where  bolts  are  shown  on  structural  steel  work 
they  are  ordinarily  conventionalized  to  the  extent  of 
omitting  the  threads.  This  is  because  they  are  ordi- 
narily standard  stock  machine  bolts. 


46 


RIVETS— STRUCTURAL  STEEL 


The  necessity  of  showing  the  dimensions  of  rivets 
and  rivet  holes  is  usually  dispensed  with  by  the  use 
of  notes.  The  dimension  and  weight  per  foot  of  stand- 
ard structural  steel  members  as  I-beams,  channels, 
tees,  etc.,  is  usually  indicated  by  a  note  on  or  alongside 
the  member  rather  than  by  dimension  lines.  The  mark 
^  used  with  such  notations  indicating  pounds.  See 
Structural  Steel  Member,  Plate  VIII. 

The  crowded  space  for  dimensioning  of  rivet  spac- 
ing and  other  close  parts  on  structural  work  has  led 
structural  steel  draftsmen  to  adopt  the  method  of 
placing  the  dimensioning  numeral  above  a  continuous 
dimension  line  instead  of  in  a  break  in  a  broken  dimen- 
sion line  as  is  universal  with  other  draftsmen.  This 
is  done  even  where  space  would  permit  of  the  more 
general  practice. 

Angles  are  never  indicated  by  degrees  as  in  ma- 
chine work  but  are  indicated  by  their  tangents  on  a  12" 
base  lines.  This  is  the  way  the  bends  on  the  tee  brace 
on  the  drawing  Structural  Steel  Member  are  indicated, 
as  the  reader  will  note. 


The  reader  will  do  well  to  give  considerable  study 
to  this  drawing ;  note  that  the  cross  section  shape,  over 
all  dimensions  and  weight  of  the  various  parts  per 
linear  foot  are  given  by  notes.  The  dimension  lines 
are  principally  for  locating  rivet  holes.  The  various 
kinds  of  rivets  are  indicated  by  proper  rivet  symbols. 
The  draftsman  has  utilized  the  privilege  of  breaking 
his  drawing  in  order  to  accommodate  it  to  the  space 
available  on  the  drawing  sheet. 

QUESTIONS    AND    PROBLEMS. 

1.  What  size  rivets  are  used  in  the  Structural  Steel  Member, 
Plate  VIII? 

2.  How  many  steel  parts  in  this  assembly? 

3.  How  long  a  piece  is  required  for  the  brace  piece? 

4.  How  much  will  the  entire  I-beam  weigh?    The  Tee  brace? 

5.  What  size  are  the  angle  pieces  on  the  right  hand  end? 

6.  Where  are  counter  sunk  rivets  used  on  this  construction? 
Are  they  chipped  flush  with  the  surface  or  left  rough? 
Which  face  is  the  countersinking  on? 

7.  What  kind  of  rivets  are  to  be  used  in  riveting  on  the 
construction  at  the  outer  end  of  the  brace? 

What  size  holes  are  these  rivets  to  go  into? 


XI.  ARCHITECTURAL  CONVENTIONS 


The  student  of  drawings  will  find  considerable  dif- 
ference between  the  drawings  made  by  architects  and 
those  made  by  mechanical  engineers.  The  architect 
goes  less  into  detail,  as  a  rule,  than  the  engineer,  leav- 
ing details  more  largely  to  the  workman.  He  does  not 
dimension  his  drawings  always  as  fully  as  is  needed  by 
the  man  who  is  to  use  them.  As  a  result  architectural 
drawings  require  more  scalings  than  machine  draw- 
ings. The  architect  will  stress  the  matter  of  appear- 
ance of  what  he  is  designing  more  than  will  the  aver- 
age engineer.  Architects  use  a  greater  number  of 
conventions  than  mechanical  engineers.  An  engineer 
uses  few  conventions  for  the  parts  he  draws,  he  draws 
everything  out  strictly  in  accord  with  the  rules  of  pro- 
jection. He  slightly  conventionalizes  screw  threads  be- 
cause they  are  small  and  hard  to  draw  accurately,  but 
the  architect  abbreviates  his  work  by  a  great  many 
conventional  representations. 

In  architectural  drawings  the  terms  plans  and  ele- 
vations are  used  in  place  of  the  terms  views  or  projec- 
tions. The  term  plan  is  used  in  place  of  top  view  or 
horizontal  projection.  A  roof  plan  is  a  top  view  of 
a  building,  a  floor  plan  is  a  top  view  of  a  floor  with 
the  walls  cut  off  about  half  way  from  the  floor  to  the 
ceiling — in  other  words  a  floor  plan  is  a  horizontal 
section  of  a  building  looking  downwards.  Elevations 


are  front  or  side  views,  and  are  often  designated  as 
north,  south,  east  or  west  elevations  as  the  case  may 
be. 

Walls  of  frame  buildings  are  conventionalized  on 
floor  plans  by  two  parallel  lines  spaced  at  a  distance 
apart  equal  to  the  thickness  of  the  walls — usually  6" 
or  8".  See  the  adjacent  wall  represented  in  the  first 
few  examples  of  windows  and  doors,  Plate  IX.  When 
masonry  walls  are  shown  on  a  floor  plan  the  lines  are 
usually  filled  in  between  with  cross  hatching.  See  ex- 
ample of  Two  Sash  Masonry  Wall  Window  and  Base- 
ment Single  Sash  Window,  Plate  IX.  Occasionally  an 
architect  fills  in  solid  between  the  wall  lines  with  a 
brush  or  pencil  instead  of  with  cross  hatching.  Where 
floor  plans  are  to  be  printed  in  books  and  magazines 
often  the  walls  are  filled  in  solid  for  frame  buildings  as 
well  as  for  masonry  buildings  as  they  show  up  better, 
but  this  is  rarely  if  ever  done  on  blueprints. 

Doors  are  usually  shown  as  single  lines.  They  are 
always  represented  as  more  or  less  open.  The  arcs 
shown  in  the  example  on  Plate  IX,  are  often  drawn 
dotted. 

Windows  are  sometimes  drawn  with  one  line  rep- 
resenting a  sash  and  sometimes  with  two  so  that  it  is 
not  always  certain  whether  a  double  line  represents 


48 


GAS  AND    ELECTRIC    SYMBOLS 

W      Telephone,  private   service 

M     Telephone ,  public  ser  vie  e 

9.    Bell  Outlet 

o    Buz.z.er  Outlet. 

132  Push  Button  Outlet,  numeral  indicates  number  of  pushes. 
-O     Annunciator,  numeral  indicates    number  of  points 
H      Speaking  Tube 

H      Door  Opener 

GJ     Electric   Ceiling  Outlet.    Z  lights 

mi    Electric  and  Gas  Ceiling  Outlet.  Z_  each 

U2    Gas  Ceiling  Outlet,  Z  lights. 
}Q3     Electric  Wall  Outlet,  Z  lights. 

HJif    Electric  and  Gas  (/Vail  Outlet.  4  electric  and  Z  gas  lights 
m  ?    Gas  Wall  Outlet,  Z  lights 
fQ      Electric  Wall  or  Baseboard  Receptacle    Outlet. 

BI      Electric    Floor  Outlet ,  4  lights 

21     Electric  Drop  Cord. 

Q     Special  Outle  t  for  fighting,  heating  and aower- current 

as  described  in   specification . 
COO     Ceiling  Fan  Outlet. 
*  S'  IV    Four  Single  Pole   Switches 
*S*     Switch.  ±  way 
mm      Distribution   Panel 

^^     Motor  Outlet,  numeral  indicates  horsepower. 
^3     Motor  Control  Outlet 


Rheostat 

Variable  Resistance 

tnduc ti ve  Resistance . 
— /P—    Crossing    Wires 
~~^ —   Joined  Wires 
~°W      Ground 

Transformer 


ARCHITECTURAL   FLOOR.   PLAN   CONVENTIONS 
WINDOWS  AMD  DOORS 


Outside  Doors,   sizes 
Shown. 


Double  Sash  Windows, 
showing    two  methods 


Inside   Single  Door  Double  Casement  Window 


Double  Swin<g  Door 


"Double  .Swinging  Doors 


Arch  or  Cased  Opening 


Double  Trench  Window 


Single 
Window 


Two  Sxsh  Masonry  W*ll 
Window 


Mullion  Window 


Colonnnde  with  Floor    Columns 


with  Pedesta.1  Columns 


Dl .,«...     TV 


50 


BLUE  PRINT  READING 


a  single  or  double  sash  window.  The  line  representing 
the  sill  edge  is  not  always  shown  on  frame  building 
plans  but  always  shown  on  plans  for  masonry  build- 
ings. 

Dotted  lines  on  a  floor  plan  do  not  always  repre- 
sent something  hidden  under  the  floor,  but  usually 
represent  something  above.  Note  the  dotted  lines 
apart  of  the  conventional  representations  of  the 
Arched  or  Cased  Opening  and  the  examples  for  colon- 
nades. These  dotted  lines  represent  that  part  of  the  wall 
extending  over  the  openings.  The  drawing  Plan  of 
Small  Building,  Plate  X  shows  where  the  draftsman 
has  differentiated  between  lines  representing  that 
which  is  above  and  that  which  is  below  the  floor  by 
using  plain  broken  lines  for  one  and  dot  and  dash  lines 
for  the  other. 

Note  in  the  chimney  examples  how  a  tile  lined  chim- 
ney is  shown.  Where  building  laws  require  chimneys 
to  be  lined  or  the  matter  is  covered  in  the  specifications 
this  is  not  always  drawn  in.  Some  architects  state' 
the  size  of  the  flue  opening  by  figures  arranged  thus, 
8/8,  8/12,  as  the  case  may  be,  placed  in  the  center  of 
the  chimney  drawing. 

Lines  similar  to  those  showing  the  lining  of  the 
chimney  appear  on  the  inside  of  the  wall  drawing, 
Two  Sash  Masonry  Wall  Window,  Plate  X.  These 


show  that  this  wall  is  either  sheathed  or  plastered  up 
on  the  inside.  Note  that  it  is  not  so  shown  on  the 
drawing  Basement  Single  Sash  Window. 

Fireplace  drawings  on  floor  plans  do  not  show  the 
flue  to  the  fireplace  but  may  show  flues  coming  up 
from  the  basement  or  story  below  along  with  the  ma- 
sonry of  the  fireplace.  Neither  these  flues  nor  ash 
dumps  must  be  interpreted  as  flues  to  the  fireplace. 
The  flue  to  the  fireplace  will  appear  only  in  the  plan 
of  the  floor  or  roof  above. 

Plumbing  conventions  are  usually  pictorial  enough 
to  readily  be  recognized,  but  gas  and  electrical  con- 
ventions are  not  quite  so  easy  to  understand  and 
should  be  carefully  studied. 

Stairs  are  readily  recognized  but  it  is  not  always 
clear  whether  the  stairs  go  up  or  down  from  the  floor. 
The  cue  is  in  the  arrow  with  its  accompanying  word 
Up  or  Down — sometimes  abbreviated  U  or  D.  Re- 
member the  arrow  leads  from  the  floor,  the  plan  of 
which  you  are  reading.  Do  not  imagine  that  an  arrow 
marked  down  could  be  reversed  in  direction  and 
marked  up  and  mean  the  same  thing.  In  the  first  case 
the  stair,  if  in  a  one  story  house,  would  lead  to  the 
basement  and  in  the  second  case  lead  to  the  attic. 

Where  pipe  is  shown  in  large  enough  scale,  as  in 
detail  drawings,  pipes  are  shown  by  two  parallel  lines, 


ARCHITECTURAL   FLOOR   PLAN    CONVENTIONS 
STAIRS  ,  CHIMNEYS  FIREPLACES  «-FLUMBIK&  FIXTUKES 


Plat?  of  Small 
Building 


MOTE 

Broken  lines  on 
a  building  f>3an 
may   re)»-e«enl 
parlj  eilber 
above   or  belovr 


a  2"oo' Jei»<  f 

_f»10'-lt'O.C.  _ 

Double  Arrows 
on  a  Floor  Plan 
Show  Way  Floor 
Joxst?  Run 


Chimney. 
Nolininj. 


Chimney, 
Tile  lined. 


ao 


Double  Tine 
Chimo'ey, 
No  Lining. 


LIVA  lories 


Pipes 


Fifeplact   Wilh  Flue 
From  Slory  Below 


sh  Dump 


Fireplace    Wlh 
A^h  Dump 


Corner 

plact  Wilh  Tile 

Outer  Hearth. 


CloSelJ 


Balh  Tu1> 


Roll  Biro  Sink 


& 


Plain  Open  Stairi 
Going  Up  From 
Floor  Shown  on 
Pi  aw. 


Boxe 


ng  Down 


form  Open 

and  Boxed 
Stair  unde 
nealh  Gore^  Down 


Plate  X 


51 


BLUE  PRINT  READING 


as  the  pipe  border  about  Plate  XI.  Where  pipe  and 
scale  are  large  enough  the  pipe  fittings  are  more  or 
less  accurately  drawn  true  to  projection  but  as  these 
are  reduced  to  smaller  size  on  drawings,  draftsmen 
more  or  less  conventionalize  the  drawings  of  these  fit- 
tings. They  are  usually  near  enough  like  the  true 
projections  as  to  be  readily  recognized  by  one 
familiar  with  pipe  fittings.  A  study  of  the  Double 
Line  Pipe  Symbols  shown  on  this  plate  will  make  it 
clear  that  the  more  common  fittings  can  easily  be 
memorized.  Draftsmen  usually  mark  by  a  note  any 
unusual  fittings.  Note  that  flanges  are  always  plainly 
indicated  on  flange  fittings. 

It  should  be  understood  that  these  symbols  are  not 
universally  used  by  draftsmen,  but  there  is  not  varia- 
tion enough  but  that  if  one  is  familiar  with  these  he 
will  find  little  confusion  from  reading  the  drawings  of 
different  draftsmen.  It  is  like  reading  the  handwriting 
of  various  persons.  Each  writer  has  his  individual 
style  but  even  a  poor  reader  can  read  the  writing  of 
any  good  penman. 

Where  the  scale  is  small  draftsmen  use  the  Single 
Line  Symbols  shown  on  the  left  side  of  the  plate. 
Even  where  the  scale  is  large  enough  so  that  double 
line  pipe  symbols  could  be  used,  draftsmen  very  often 


use  the  single  line  symbols  because  of  its  simplicity. 
In  this  system  the  fittings  are  much  more  convention- 
alized than  in  the  double  system. 

Ordinarily  the  solid  line  is  used  to  represent  a  pipe 
but  where  it  is  desired  to  differentiate  between  the  flow 
and  return  lines  a  broken  line  is  used  for  the  return. 
The  direction  of  flow  of  the  water  or  stream  is  indi- 
cated by  an  arrow.  The  inside  diameters  of  the  pipes 
are  indicated  by  numerals  placed  alongside.  Note  that 
several  fittings  have  more  than  one  way  of  being  repre- 
sented. There  are  still  other  variations  used  by  some 
draftsmen  but  if  the  reader  is  familiar  with  these 
shown,  variations  will  not  be  confusing.  Note  the 
difference  between  the  representation  of  a  plan 'of  the 
tee  drop  and  a  tee  rise  also  the  plan  representation  of 
a  turn  up  and  a  turn  down. 

The  Typical  Radiator  Group  shown  both  in  plan  and 
elevation  on  the  right  of  the  plate  illustrates  well  how 
these  symbols  appear  in  use.  Note  that  if  you  are 
familiar  with  the  meaning  of  the  various  symbols  you 
can  get  the  same  information  from  either  plan  or  ele- 
vation. Probably  the  only  thing  that  cannot  be  told 
from  one  and  not  the  other  is  the  lengths  of  some  of 
the  numerous  pipes.  In  practice  a  draftsman  would 
ordinarily  furnish  but  one  drawing  either  a  plan  or  an 
elevation. 


Sttam  mdinorflc 
Rtlurn  main.stMt 
Hoi  Wd  ter  main  or 

Air  line!  Arrow  in 
fditccltou 
I^i  fir     Jlhtpipt- 

Screwed  unions,  i 
Flangzd  unions 
GlobtvdlveB       H 
Gate  valve. 
Check  valves 

T«.t  and  EU         r 

long  sweep 

Cross.  T«c  and 
Ell.  doge. 
4 
Tct  drop  and 
rise.,  plan  acd      ' 
clcvalion 

Turn  down 
and  up.  plan       ' 
and  elevation 

Branch  from      1^ 
undur  main,~*' 
plan  view 
Branch  from 
top  of  main, 
plan  view. 
Crossing  pipes  not 
connecting.  5ec 
cross  cln  above 

IE    PIPE    SYMB 

"n 

wr 
norwaler    ^ 
flow 

lica\esflow   « 
numerals     • 
iae               1 

methods       J 

/ 

rf,       *U 

•      lf.F 

5—  .&  — 
-it— 

O       (rf 

Aia^le.         £ 
valves 
2melhods 

1 

\         l] 

valve 
walcr 

"*Airv«lvt 
J  #tean? 

Relurn       1 
trap 

/Dirl 
pocket 

J>  rioor 
^~ltap 
plan  and 
elevation 

OLS 

I 

1 

T  't 

rr 

T 

', 

^j 

i 

i-r 

SI 

f 

NGLE  Lt> 

Flanged  tee 

Flangtd 
union 


valve. 


Coupling 


)  Union 


valve. 

Lift 
checK 


B-i 


VJ- 


Tce 


Hot  air  furnace  fr  pipes 


lo  room* 
above 


Wall  regtsl*ri.  frame  wall 


majonru 


,  plan  XT elcva bon 


|    Floor  register 


o  Radiator  on 
plans.  2  pipe 

Radial  or  on 
\    elevations 

N-m.-.l.  InllcU* 

S4.fl  tiitttlaw  IHrf4U 


HEATING  AND 
VENTILATING  SYMBOLS 


s  / 


TYPICAL  RADIATOR  GROUP 
IN  PLAN  AND  ELEVATION 


Plate  XI 


S3 


54 


BLUE  PRINT  READING 


For  the  sake  of  study  we  will  follow  the  pipe,  using 
the  plan  drawing  only,  from  its  beginning  at  the  lower 
right  corner  until  its  return.  The  student  will  do  well 
to  follow  the  line  with  a  pencil  point  as  he  reads. 

The  first  fitting  we  encounter  is  an  ell  by  means 
of  which  the  pipe  turns  to  the  left.  As  we  follow  the 
line  to  the  left  we  pick  up  the  dimensions  of  the  pipe, 
learning  that  it  is  a  3^"  pipe.  The  next  symbol  is  one 
showing  a  branch  from  the  top  of  the  main  we  have 
been  following.  There  is  nothing  to  show  how  much 
this  branch  rises  before  it  branches  off.  That  can 
only  be  read  by  referring  to  the  elevation  drawing. 
Following  this  branch  we  discover  that  the  branch  is 
smaller  than  the  main,  being  but  ll/2"-  A  tee  separates 
the  line.  Following  each  branch,  past  an  ell  in  one, 
we  reach  symbols  indicating  risers.  Extending  back- 
ward and  to  the  right  from  these  risers  we  find  fine 
lines  which  represent  the  risers  as  though  they  stood 
up  from  the  surface  of  the  paper  and  were  leaning  out 
of  the  way  of  our  view  of  the  rest  of  the  drawing. 
Note  that  the  terminal  of  each  branch  from  the  flow 
riser  is  a  numeral,  indicating  the  number  of  square 
feet  of  radiating  surface  that  the  radiator  there  is  to 
have.  On  following  the  return  branches  and  return 
riser  back  we  note  that  these  return  pipes  are  the  same 
size  as  the  flow  pipes.  When  the  return  reaches  the 


point  where  it  distinctly  becomes  a  return  main  the 
draftsman  uses  the  return  main  symbol  of  a  broken 
line. 

At  the  upper  central  part  of  the  plate  is  shown  a 
hot  air  furnace  and  pipes  as  they  would  appear  on  a 
basement  plan.  If  these  were  shown  on  the  first  floor 
plan  as  they  occasionally  are,  they  would  be  drawn 
with  dotted  lines  to  indicate  that  they  were  hidden 
beneath  the  floor.  Note  the  difference  between  the 
floor  registers  and  the  stacks.  The  pipes  terminating 
in  floor  registers  would  supply  heat  to  the  first  floor 
rooms,  while  the  stacks  would  carry  heat  to  the  second 
story  rooms. 

The  arrows  on  Heat  and  Ventilation  Registers  in- 
dicate the  direction  of  air  flow  and  consequently  whe 
ther  the  register  is  to  supply  heat  and  fresh  air  or  to 
carry  off  foul  and  cold  air. 

The  Floor  Register  is  drawn  thus  on  floor  plans 
only. 

Radiators  are  sometimes  drawn  more  elaborately 
than  here  shown  but  their  position  usually  makes  clear 
what  they  are.  On  plans  they  are  often  inked  in  solid 
and  usually  have  the  abbreviation  Rad.  printed  on 
them.  The  numerals  on  the  elevation  indicate  the 
number  of  squire  feet  of  radiating  surface  the  radiator 
is  to  have. 


ARCHITECTURAL  CONVENTIONS 
QUESTIONS    AND    PROBLEMS. 


55 


1.  Are   windows   single   or  double   sash   in   Plan   of   Small 
Buildings,  Plate  X? 

2.  What  kind  of  windows  are  indicated  in  the  House  Plan 
on  Plate  V? 

3.  Is  the  chimney  of  this  house  to  be  lined? 

4.  What  valves   do  the   radiators   in  the   Typical   Radiator 
Group  Plate  X  have?    Can  this  be  determined  from  the 
plan  view? 

5.  Why  was  it  unnecessary  for  the  draftsman  to  show  by 
arrows  the  direction  of  flow  of  the  steam  in  the  pipes 
for  this  group? 

6.  Are  all  the  radiators  of  the  Typical  Radiator  Group  of  the 
same  size? 

7.  Are  the  flow  and  return  mains  the  same  size? 

8.  Make  an  enlarged  sketch  of  the  kitchen  from  the  house 
plan  in  Plate  V  and  locate  a  hot  water  heater  in  the  cor- 
ner by  the  chimney  and  a  kitchen  sink  by  one  of  the 


windows  then  connect  the  two  by  necessary  pipe.  Con- 
ceal pipe  in  the  walls  and  under  the  floor.  Use  single 
line  conventions  and  draw  in  all  necessary  symbols. 
9.  Sketch  both  plan  and  elevation  of  a  water  system  con- 
sisting of  a  storage  tank  on  a  low  tower,  a  line  coming 
from  a  pump  house,  a  line  running  to  a  yard  hydrant 
and  one  to  a  residence.  Show  all  necessary  pipe  fittings 
by  single  line  symbols. 

10.  The  owner  of  the  house  shown  on  Plate  V  wishes  to  re- 
model it  by  building  a  wing  and  a  second  story  over  the 
old  part  and  by  placing  a  furnace  basement  under  the 
old  part.    Make  a  sketch  of  a  basement  plan  and  lay  out 
a  hot  air  furnace  heating  plan  showing  furnace  heating, 
pipes,  registers,  stacks  to  second  floor  rooms,  etc. 

11.  Lay  out  necessary  piping  to  run  a  hot  water  line  from 
the  furnace  to  the  kitchen  and  to  a  bathroom  to  be  lo- 
cated on  the  second  story  directly  over  the  two  closets 
shown  on  the  plan.    You  use  single  line  system. 


XII.     STUDY  OF  A  SET  OF  HOUSE  PLANS 


The  use  of  the  word  plans  in  the  title  to  this 
chapter  is  in  accord  with  the  quite  common  usage  of 
calling  all  of  a  set  of  architectural  drawings  plans  re- 
gardless of  the  fact  that  the  set  may  be  composed  of 
many  drawings  which  are  not  plans  but  are  elevations 
or  detail  drawings.  In  this  case  ths  set  consists  of 
Front  Elevation,  Side  Elevation,  Floor  Plan,  Roof  and 
Attic  Plan,  Basement  Plan,  Masonry  Details,  and 
Cabinet  Details— Plates  XII  to  XVIII. 

Not  all  of  the  information  needed  by  a  workman 
on  the  building  can  be  secured  from  the  drawings. 
Such  drawings  are  always  accompanied  by  a  set  of 
written  specifications  which  specify  such  matters 
as  kind  and  quality  of  materials  to  be  used,  meth- 
ods of  workmanship,  etc.,  which  can  not  be  shown 
on  the  drawings.  As  this  work  is  on  the  study  of  draw- 
ings and  not  specifications  mention  of  specifications 
is  made  simply  that  attention  may  be  called  to  the 
fact  that  drawings  and  specifications  should  ordinarily 
be  studied  together. 

The  study  of  a  set  of  drawings  can  not  advan- 
tageously be  studied  as  the  specifications  can  by  be- 
ginning with  the  first  sheet  and  reading  the  set  through 
one  sheet  after  another.  Instead  we  look  the  entire 
set  through  to  get  the  main  characteristics  of  the  build- 
ing in  mind  and  then  by  referring  back  and  forth  from 


sheet  to  sheet  we  study  out  detail  after  detail  until  all 
the  details  of  construction  are  in  mind. 

Perhaps  the  term  plans  is  used  so  commonly  to  in- 
clude all  the  drawings  of  a  set  because  most  of  the 
dimensions  and  detailed  information  is  found  on  the 
floor  plans.  However,  the  general  type  of  the  struc- 
ture is  usually  more  clearly  shown  by  the  elevations. 
For  this  reason  we  will  look  over  the  elevations  first 
in  this  study,  but  not  give  them  a  very  thorough  study 
until  we  have  looked  through  the  entire  set.  If  the 
student  has  not  already  done  so,  he  should  pause  here 
in  his  reading  and  spend  a  few  minutes  looking  over 
the  drawings  of  the  Residence— Plates  XII  to  XVIII. 

This  preliminary  study  of  the  entire  set  should 
have  told  the  student  that  it  is  a  complete  set  of  work- 
ing drawings  of  a  story  and  a  half  frame  residence, 
having  as  prominent  characteristics,  a  large  front 
porch  with  brick  buttresses  to  the  columns,  a  three 
gable  roof,  a  small  ornamental  shed  dormer  window 
on  the  roof,  an  outside  fireplace,  a  screened  back  porch, 
five  rooms  on  the  main  floor — living  room,  dining 
room,  two  bedrooms  and  a  kitchen — ,  a  basement  with 
hot  air  heating  system,  a  servants'  room  and  a  large 
storeroom  on  the  second  floor,  and  built  in  buffet  and 
colonnade  book  case. 


56 


Plate  XII 


57 


58 


BLUE  PRINT  READING 


Probably  also  he  will  have  picked  up  such  details 
as,  that  the  front  porch  steps  are  of  concrete,  that 
there  are  louvres  in  the  gables,  that  exposed  rafter 
cornice  is  to  be  used,  that  the  dining  room  is  to  have 
beamed  ceilings,  that  there  is  a  bath  room  with  three 
fixtures  in  it,  that  the  basement  stairs  are  directly 
under  the  second  story  stairs,  that  the  furnace  room 
does  not  extend  under  the  entire  house,  that  only  part 
of  the  second  story  is  floored,  that  the  porch  buttresses 
are  hollow,  that  both  brick  and  concrete  is  used  in 
the  foundation  walls,  and  many  other  similar  pieces 
of  information. 

If  the  student  will  turn  his  attention  to  the  front 
elevation,  Plate  XII,  the  author  will  try  to  lead  him  in 
a  more  thorough  study  of  this  drawing.  Note  that  the 
house  rests  on  a  brick  foundation  but  that  the  fine  dots 
covering  the  steps  show  that  the  steps  are  to  be  of  con- 
crete. There  are  four  brick  column  piers  but  not  all  of 
them  support  columns.  These  piers  are  capped  by  con- 
crete caps.  The  horizontal  sketchy  lines  on  the  front 
face  of  the  building  show  it  to  be  of  wood  siding  and 
not  of  plaster  or  stucco.  The  few  scattered  shingles 
drawn  on  the  roof  as  well  as  the  word  "Shingles" 
shows  the  character  of  the  roofing  material. 

The  exposed  rafter  ends  along  the  front  of  the 
porch  roof  show  that  an  open  rafter  cornice  is  to  be 


used.  The  student  will  make  a  mental  note  of  the 
character  of  the  windows,  front  door,  porch  rail  and 
other  details. 

The  student  should  study  the  Porch  Section  along 
with  the  Front  Elevation.  Such  sections  are  drawn  by 
draftsmen  before  drawing  the  elevations.  These  sec- 
tions establish  heights  of  floors,  ceilings,  cornice,  and 
many  other  details. 

Perhaps  a  study  of  this  section  will  give  the  stu- 
dent his  first  information  that  the  porch  roof  is  not 
the  same  pitch  as  that  of  the  main  roof.  It  is  the  only 
source  on  the  entire  set  of  drawings  from  which  he 
can  learn  the  porch  ceiling  height. 

Many  important  details  of  construction  are  to  be 
learned  from  this  section — size  and  spacing  of  studs, 
rafters,  joists,  etc.,  are  all  important  construction 
details. 

When  the  student  turns  to  the  study  of  the  Side 
Elevation,  Plate  XIII,  he  secures  additional  informa- 
tion regarding  the  shape  of  the  roof.  He  learns  that 
the  house  is  larger  from  front  to  rear  than  from  side 
to  side.  He  notes  that  the  windows  are  grouped  in 
threes  as  a  rule  but  finds  no  figures  to  indicate  their 
size.  Two  single  light  windows  near  the  rear  show 
hidden  edge  lines  extending  up  over  them.  He  will 
likely  understand  these  lines  to  indicate  pockets  in  the 


OF 

BEMQE 


Plate   XIII 


60 


BLUE  PRINT  READING 


wall  for  the  windows  to  slide  up  into  showing  that 
they  are  jib  windows. 

In  studying  the  front  porch  the  student  will  note 
something  which  may  have  escaped  him  in  his  study 
of  the  front  elevation  that  brick  buttresses  extend  out 
alongside  of  the  front  steps. 

A  little  study  of  the  rear  of  the  house  shows  a 
screened  porch  and  a  flight  of  back  steps  evidently  of 
wood  construction. 

When  the  student  turns  his  attention  to  the  Floor 
Plan,  Plate  XIV,  he  may  find  it  such  a  maze  of  lines 
as  to  require  considerable  study  to  make  these  lines 
convey  a  definite  meaning  to  him.  Picking  out  the 
names'  of  the  rooms,  referring  back  to  the  elevations 
and  to  the  plates  of  architectural  conventions  in  the 
next  preceding  chapter  all  will  help  to  make  these 
lines  stand  for  definite  walls,  doors,  windows,  fix- 
tures, etc. 

When  he  examines  the  front  porch  he  will  doubt- 
less note  that  the  masonry  buttresses  at  the  corners 
of  the  porch  are  represented  differently  from  the  two 
central  ones.  Reference  to  the  elevations  will  make  it 
clear  why  they  are  not  alike.  Notes  by  the  front  win- 
dows show  the  size  of  glass  in  these  windows  and 
that  all  are  two  light  windows.  The  fact  that  these 
windows  are  shown  by  two  lines  instead  of  one  shows 


that  they  are  double  hung — two  sash — windows.  The 
student  should  study  all  the  windows  and  note  their 
size,  number  of  sashes,  method  of  hanging,  etc. 

The  note  by  the  front  door  shows  its  size.  The 
student  should  note  whether  the  other  doors  are  all 
this  size.  He  should  discover  whether  or  not  any  are 
double  acting  and  if  there  are  any  cased  openings 
having  no  doors. 

Near  the  center  of  the  Living  Room  the  student 
will  note  a  double  end  arrow  indicating  the  direction 
the  floor  joists  are  to  run.  Study  of  similar  arrows  in 
other  parts  of  the  house  will  show  that  there  is  one 
place  where  the  joists  change  direction.  If  he  will 
refer  back  to  the  Porch  Section  he  will  find  another 
place  where  the  direction  is  out  of  the  general  arrange- 
ment though  no  arrows  indicate  it  on  the  floor  plan. 

The  student  should  study  the  electrical  symbols  in 
the  various  rooms.  Two  electric  ceiling  outlets  are 
shown  in  the  Living  Room  each  to  be  wired  for  four 
lights.  Outlets  in  other  rooms  are  to  be  wired  for  a 
various  number  of  lights.  In  one  room  he  will  find  a 
wall  outlet  instead  of  a  ceiling  outlet.  He  must  not 
mistake  the  wall  plugs  shown  in  three  or  four  rooms 
for  wall  light  outlets  nor  the  floor  plug  in  one  room  for 
a  ceiling  outlet.  He  should  locate  the  switches  to  the 


Jl 


62 


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various  lights  and  note  if  any  lights  are  drop  lights. 
He  will  note  that  by  the  front  door  are  two  two  way 
switches  controlling  the  porch  light.  At  the  opposite 
side  of  the  room  he  will  find  that  Roman  numerals  in- 
dicate three  two  way  switches.  One  of  these  two  way 
switches  sharing  with  similar  switches  on  the  oppo- 
site wall  in  controling  the  Living  Room  lights.  At  the 
opposite  side  of  the  room  he  will  find  that  Roman  num- 
erals indicate  three  two  way  switches.  One  of  these 
two  way  switches  seems  to  control  a  light  up  stairs 
since  the  connecting  wire  is  shown  running  up  the 
stairs  and  stopping  at  the  freehand  line  indicating  a 
breaking  off  of  the  stairs.  The  student  should  pick 
this  line  up  when  examining  the  upstairs  and  locate 
the  light  it  controls. 

He  should  examine  the  stair  carefully  as  these  are 
frequently  a  cause  of  confusion  and  mistaken  ideas  to 
an  inexperienced  reader  of  drawings.  The  break  line 
drawn  across  the  stair  space  and  the  two  arrows  one 
marked  "Up"  and  one  "Down"  shows  that  the  drafts- 
man has  indicated  that  two  stairs  are  to  occupy  the 
stair  well  one  going  up  from  the  main  floor  and  one 
underneath  going  down  from  the  same  floor.  It  is 
usually  well  in  reading  stairs  to  confirm  one's  reading 
by  a  study  of  the  representation  of  the  stairs  on  the 
plans  of  floors  above  and  below.  The  student  will 


therefore  do  well  to  look  back  to  the  Basement  and 
Attic  Plans. 

The  student  will  discover  by  the  note  "Beam  Ceil- 
ings" explanation  of  the  numerous  dotted  lines  in  the 
Dining  Room.  The  student  should  locate  the  buffet 
opening  into  the  dining  room,  the  back  chimney  noting 
into  which  room  the  thimble  opens,  the  kitchen  sink 
and  draining  board,  the  bath  room  fixtures. 

In  the  Bath  Room  he  should  notice  that  there  is  a 
medicine  closet  built  into  the  8"  wall  and  that  the  heat 
register  opens  from  the  wall  rather  than  through  the 
floor  as  indicated  in  most  of  the  rooms. 

The  student  should  study  the  dimensions  of  the 
various  rooms  noting  carefully  whether  the  dimensions 
read  from  the  inside,  center  or  outside  of  the  walls. 
If  he  studies  the  wall  thickness  carefully  he  will  note 
that  the  walls  are  not  all  6"  thick,  that  one  is  an  8" 
wall  and  some  are  less  than  6". 

While  studying  the  floor  plan  the  student  will  do 
well  to  turn  back  to  the  drawing  of  Cabinet  Details, 
Plate  XVIII.  In  the  study  of  these  details  he  will  get 
his  first  intimation  that  the  Dining  Room  is  to  have 
a  plate  rail  and  to  have  paneled  walls  below  the  rail. 
Here  he  will  get  minute  details  of  such  parts  as  will 
likely  be  made  in  a  cabinet  works  and  built  into  the 
house.  The  student  should  figure  out  the  number  of 


floured,  shiplap  walled1  not  rt(lcd 


Plate  XV 


63 


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drawers,  shelves,  doors,  etc.,  in  each  of  the  pieces  of 
cabinet  work  details.  He  should  note  whether  doors 
are  to  be  glazed  or  paneled. 

He  should  study  the  column  over  the  bookcase  to 
discover  whether  or  not  it  is  tapered  and  whether  it 
is  round  or  square.  He  will  find  the  answer  to  both 
these  in  the  dimensioning.  The  former  by  comparing 
the  width  given  for  the  top  and  the  bottom,  and  to 
the  latter  by  the  draftsman  having  used  the  drafts- 
man's symbols  for  square  in  connection  with  the  num- 
erals. 

When  the  student  comes  to  studying  the  Roof  and 
Attic  Plan  he  will  discover  that  the  draftsman  has 
started  with  a  roof  plan  and  then  broken  away  all  of 
the  central  part  so  as  to  show  the  rooms  on  the  sec- 
ond floor.  He  has  left  the  interfering  roof  lines  dotted. 
Where  he  has  left  the  roof  in  solid  lines  over  the  front 
of  the  house  and  at  the  rear  corners,  he  has  shown 
the  partitions  underneath  in  dotted  lines.  This  double 
use  of  dotted  lines  may  be  a  little  confusing  to  the 
student  if  he  does  not  keep  definitely  in  mind  the 
bounds  of  the  broken  out  area. 

He  will  note  that  the  second  floor  space  is  divided 
off  into  a  large  Store  Room,  a  Servant's  Room,  Closet 
and  four  closed  in  attic  spaces.  Notes  indicate  the 
rooms  to  be  floored  and  walled  up.  Presumably  since 


there  is  no  instruction  to  floor  and  sheath  them  the 
attic  spaces  are  to  be  left  unfinished. 

The  student  should  study  the  windows  as  there 
are  some  unusual  features  indicated  regarding  them. 
Reference  back  to  the  Front  and  Side  Elevations  will 
help  to  understand  them. 

The  electric  light  shown  in  the  center  of  the  Store 
Room  is  seen  to  be  controlled  by  a  two  way  switch  at 
the  head  of  the  stairs.  There  is  also  a  wire  running 
down  stairs  from  this  light,  evidently  to  a  switch  at 
the  down  stairs  door  to  the  stairs.  He  will  find  a 
switch  controlled  light  in  the  Servant's  room  and  a 
drop  cord  in  the  Closet.  A  floor  register  in  the  Ser- 
vant's Room  shows  that  this  room  is  heated  from  the 
basement  furnace. 

The  Basement  Plan,  Plate  XVI,  must  be  studied 
in  conjunction  with  the  Masonry  Detail  sheet,  Plate 
XVII.  The  basement  proper  is  discovered  to  be  but 
one  room,  a  furnace  room  with  a  coal  bin  in  one  end. 
The  method  of  sectioning  the  walls  shows  that  the 
Furnace  Room  walls  are  of  concrete  except  the  out- 
side wall.  The  outer  walls  are  of  brick,  the  sectioning 
indicates.  There  are  three  sections  cutting  the  furnace 
room  wafts — sections  AA,  BB  and  CC.  The  student 
must  refer  to  these  detailed  sections,  Plate  XVII. 
These  section  details  give  him  the  depth  and  thickness 


To  *cwer 


Plate   XVI 


66 


BLUE  PRINT  READING 


of  the  Furnace  Room  walls  and  also  causes  a  modifica- 
tion of  his  first  impression  regarding  the  outside  fur- 
nace room  wall.  He  discovers  that  this  wall  is  brick 
only  above  the  grade  line.  The  section  CC  calls  his 
attention  to  the  fact  that  the  stair  well  floor  is  slant- 
ing and  not  level  with  the  basement  floor.  It  also 
shows  that  the  walls  of  the  well  are  not  the  same 
thickness  as  the  regular  basement  walls. 

The  outside  wall  is  detailed  by  the  Section  DD, 
which  gives  the  thickness  and  height  above  the  foun- 
dation, the  material  and  dimensions  of  the  foundation, 
and  also  the  size  of  the  sill  to  go  on  the  wall. 

Piers  are  used  to  support  such  sills  as  have  no  sup- 
porting walls.  Only  one  of  these  is  fully  dimensioned 
on  the  plan  but  as  it  is  marked  with  the  word  "Typi- 
cal" the  student  will  understand  that  all  piers  are  to 
be  of  the  same  size.  The  detail  drawings  Typical  Pier, 
Plate  XVII,  furnishes  such  dimensions  as  are  not 
given  on  Plate  XVI.  The  student  will  note  this  detail  is 
an  elevation  and  not  a  cross  section,  even  the  founda- 
tion. He  will  discover  in  the  size  of  the  sills  which 
go  on  these  piers  the  explanation  of  why  these  piers 
are  not  as  high  as  the  foundation  wall. 

In  the  study  of  the  fireplace  the  student  will  get 
most  of  his  information  from  the  detail  drawing.  Little 
is  to  be  learned  from  the  foundation  plan  except  its 


location  and  the  purpose  of  the  extra  flue.  The  extra 
flue  is  seen  to  serve  the  furnace  located  in  the  Furnace 
Room.  The  detail  drawing,  however,  is  profuse  in  in- 
formation given.  It  shows  all  the  requisite  dimensions, 
the  concrete  foundation,  that  it  is  to  have  ash  dump, 
clean  out  door,  and  a  damper,  that  it  is  to  be  lined  with 
fire  brick,  that  the  hearth  is  concrete  underneath  the 
brick,  that  the  mantle  shelf  is  of  wood  and  many  more 
bits  of  information  essential  to  the  building  of  the 
fireplace  in  accord  with  the  architect's  ideas. 

The  student  should  notice  sections  EE,  FF,  and 
GG,  not  only  studying  the  details  but  locating  them 
on  the  plan.  He  will  observe  that  the  line  locating  ttie 
section  of  GG,  on  the  plan  is  not  a  straight  line. 

The  draftsman  has  seen  fit  to  show  the  porch 
column  in  this  section  though  it  is  not  a  masonry  de- 
tail and  might  for  that  reason  have  been  more  properly 
placed  among  the  Cabinet  Details.  It  helps,  however, 
to  illustrate  a  statement  made  in  a  preceding  chapter 
that  all  of  a  set  of  drawings  must  be  studied  together. 
A  mill  man  figuring  on  the  mill  work  for  this  building 
could  claim  no  excuse  from  the  drawing's  standpoint  if 
he  neglected  to  figure  on  the  porch  columns  because 
they  are  not  shown  on  the  cabinet  detail  sheet,  any 
more  than  the  electrical  contractor  could  excuse  a 
possible  overlooking  of  the  basement  light. 


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Plate  XVII 


67 


68 


BLUE  PRINT  READING 


The  student  should  trace  out  the  heating  pipes  and 
check  them  up  with  the  registers  shown  on  the  floor 
plans.  He  will  observe  that  there  are  certain  rooms  to 
which  no  pipes  run. 

He  should  carefully  follow  the  water  and  sewer 
pipes.  If  he  will  follow  the  water  pipe  as  it  comes 
under  the  house  from  the  front  he  will  note  that  it  is 
1"  in  diameter,  that  after  coming  under  the  porch  wall 
a  24"  riser  extends  up  and  turns  out  through  the  wall 
to  a  hose  cock.  As  the  main  passes  the  Furnace  Room 
a  tee  takes  off  a  y2"  pipe  to  supply  a  cock  in  the  Fur- 
nace Room.  At  the  rear  of  the  building  the  student 
should  continue  following  these  pipes,  possibly  listing 
the  necessary  connections.  He  may  find  it  necessary 
to  refer  back  to  Plate  XI  to  refresh  his  memory  re- 
garding some  of  the  pipe  symbols. 

The  sewer  pipes  are  rendered  in  double  lines,  being 
large  enough  for  the  draftsman  to  readily  draw  them 
that  way.  The  student  should  differentiate  between 
the  cast  iron  and  clay  tile  pipes,  abbreviated  C.  J.  and 
C.  T. 

The  student  will  have  discovered  many  things  not 
mentioned  above,  many  things  that  print  cannot  well 
make  clear,  and  there  will  doubtless  be  plenty  of  in- 
formation he  can  acquire  by  further  study.  He  should 
secure  sets  of  other  building  plans  and  study  them 


carefully.  He  will  find  considerable  individuality  in 
the  way  different  architects  express  their  ideas  in 
their  drawings  just  as  authors  differ  in  expressing 
their  ideas  in  their  writing  but  if  the  student  can  read 
thoroughly  the  drawing  of  one  good  draftsman  the 
individual  methods  of  other  draftsmen  will  cause  him 
no  trouble.  QUESTIONS. 

1.  Are  either  of  the  porches  screened,  and  if  so,  which? 

2.  Of  what  material  are  the  front  steps  to  be  made? 

3.  What   do   the   three   long   wavy   freehand   lines    on    the 
Roof  and  Attic  Plan  indicate? 

4.  What  is   the   long   dashed  line   on   the   Roof  and   Attic 
Plan,  which  extends  vertically  entirely  across  the  draw- 
ing approximately  midway  from  right  to  left? 

5.  Are  the  Attic  spaces  to  be  floored? 

6.  How  many  porch  columns  must  the  mill  man  figure  on 
furnishing? 

7.  Which  way  do   the   floor  joists   under  the   living   room 
run? 

8.  Do  the  porch  joists  run  the  same  way  as  the  main  floor 
joists? 

9.  Is  there  anything  to  indicate  whether  or  not  the  ceiling 
joists  are  to  run  the  same  way  as  the  floor  joists? 

10.  From  which  room  would  one  go  in  going  down  stairs? 
Up  to  the  Store  Room? 

11.  Is  the  basement  window  one  or  two  light? 

12.  What  means  are  provided  for  enabling  one  to  get  under 
the  house  to  the  pipes,  etc.? 

13.  Are  all  windows  two  light  and  if  there  are  any  excep- 
tions, name  them? 


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Plate  XVIII 


69 


70 


BLUE  PRINT  READING 


14.  Are  the  small  kitchen  windows  jib  or  casement  hung? 
(See  Side  Elevation.) 

15.  How  are  the  windows  by  the  fireplace  hung? 

16.  What  distinguishes  the  kitchen-dining  room  door  from 
all  the  others? 

17.  What  doors  are  6'  6"  high? 

18.  Is  there  a  plate  rail  in  the  dining  room? 

19.  What  kind  of  a  wall  separates  the  down  stairs  closets? 

20.  Is  the  wall  above  the   colonnade   opening  between  the 
!      living  room  and  the  dining  room,  the  thickness  of  the 

colonnade  buttress  or  is  it  the  same  as  the  other  walls? 

21.  What  length  and  width  is  the  front  porch  floor? 

22.  What  is  the  length  and  width  of  the  bath  room? 

23.  How  wide  is  the  stair  well? 

24.  What  length  and  width  is  the  furnace  room?    Its  height? 

25.  If  the  porch  balusters  are  24"  long,  how  many  and  of 
what  material  would  the  Contractor  figure  on  in  making 
them? 

26.  What  size  are  the  main  outside  wall  sills?     The   mid- 
sills?     The  front-porch  sills? 

27.  What  width  cornice   has  the   main   part  of   the   house? 
Is  the  dormer  cornice  of  the  same  width? 

28.  What  is  the  length  of  run  of  the  upstairs  stairs?    It  will 
require  comparison  of  both  floor  plans  and  scaling  to 
determine  this. 

29.  How  many  flues  are  there?     What  size  are  they?     Are 
they  tile  lined? 

30.  Does  the  brick  foundation  wall  under  the  front  porch 
extend  back  of  the  steps? 

31.  Of  what  material  is  the  outside  wall  to  the  furnace  room 
made?    Is  it  of  the  same  material  above  grade  as  below? 

32.  What  does  the  small  rectangle  in  the  center  of  the  fire- 


place on  the  Floor  Plan  indicate?    Confirm  your  answer 
by  study  of  the  Fireplace  Detail. 

33.  Does  the  fireplace  have  a  damper?  Cleanout?  Ashdump? 

34.  Is  it  to  be  lined  with  fire  brick? 

35.  Does  the  fireplace  chimney  extend   out  into  the  living 
room? 

36.  What  keeps  ashes  falling  through  the  ash  dump  from 
getting  under  the  house? 

37.  If  the  weight  of  the  fireplace  should  cause  it  to  settle 
would  the  outer  hearth  settle  with  it? 

38.  Of  what  material  is  the  fireplace  mantle  shelf? 

39.  Why  was  it  necessary  for  the  architect  to  place  a  pier 
under   the   wall   between   the   bath   room   and   the   back 
porch? 

40.  Are  there  any  two  way  light  switches? 

41.  Are  there  any  gas  lights  provided? 

42.  Are  any  of  the  lights  to  be  drop  lights? 

43.  Where  is  the  switch  to  the  basement  light  located? 

44.  Where  is  the  store  room  light  controlled  from? 

45.  What  provision  is  made  in  some  of  the  rooms  for  con- 
necting up  fans,  special  electric  lights,  etc? 

46.  What  does  the  little  square  with  a  figure  4  in  it  located 
at  the  exact  center  of  the  living  room  indicate? 

47.  What  does  the  Character  S2III  near  the  door  to  the  up- 
stairs indicate? 

48.  What  rooms  have  no  heat  registers? 

49.  Where  is  the  furnace  cold  air  to  come  in  at? 

50.  How  is  the  servant  room  to  be  warmed? 

51.  What  size  sewer  pipe  serves  the  house?     Water  main? 

52.  What   size   pipe   furnishes   water   to   the    kitchen   sink? 
What  size  is  the  drain  pipe? 

53.  How  many  cocks  are  provided  for  yard  hose  service? 

54.  Is  a  hot  water  piping  system  to  be  provided? 


XIII.     STUDY  OF  THE  BENCH  GRINDER 


In  the  study  of  a  set  of  drawings  consisting  of  an 
assembly  and  details,  it  is  always  best  to  begin  one's 
study  of  them  by  a  study  of  the  assembly  drawing 
first.  Doing  this  gives  one  an  idea  of  the  whole  ma- 
chine— or  whatever  the  object  is — so  that  the  details 
are  more  readily  understood. 

The  student  will  therefore  begin  his  study  of  the 
drawings  of  the  Bench  Grinder  by  a  study  of  the  as- 
sembly first — Plate  XIX.  Here  he  finds  all  the  parts 
of  the  machine  assembled,  each  piece  occupying  its  in- 
tended place.  He  will  at  once  recognize  that  it  is  a 
common  two  wheeled  type  of  bench  grinder  intended 
to  be  mounted  on  a  bench  or  pedestal.  As  he  studies 
it  over  he  will  soon  realize  that  there  is  a  little  differ- 
ence between  the  two  ends  and  investigation  shows 
that  different  types  of  rests  are  used  for  the  different 
wheels.  Perhaps  the  machine  is  made  with  either 
type  of  rest  and  the  draftsman  has  made  one  assembly 
show  both  arrangements.  This  matter  can  be  settled 
when  the  student  gets  to  studying  over  the  detail 
drawings,  because  the  detail  drawings  will  show  the 
number  of  each  part  required  for  each  machine. 

Some  details  ordinarily  on  detail  drawings  are 
omitted  on  assembly  drawings.  On  this  drawing  the 
student  will  note  that  there  are  no  dimension  lines 
except  three  or  four  over  all  dimensions  to  give  an 


idea  of  the  size  of  the  grinder.  Draftsmen  will  some- 
times put  on  an  assembly  drawing  dimensions  which 
might  be  of  use  to  the  assembling  machinist.  Evident- 
ly this  draftsman  considered  that  the  overall  dimen- 
sions all  that  were  necessary  on  the  bench  grinder. 
There  are  no  marks  indicating  finish  nor  notes  in- 
dicating the  kind  of  materials.  Very  few  hidden 
edges  are  indicated.  Some  necessary  parts  not  among 
the  detail  drawings  such  as  stock  cap  screws,  set 
screws,  oil  cups,  etc.,  are  shown  in  the  assembly  only. 

It  will  be  noticed  that  many  details  of  construction 
cannot  be  interpreted  from  the  assembly  drawing  be- 
cause the  draftsman  has  had  to  leave  out  these  details 
to  prevent  confusion  of  lines.  For  instance ; — there  is 
almost  no  information  given  regarding  the  spindle  on 
which  the  grinding  wheels  are  mounted. 

The  student  will  do  well  now  to  glance  over  the 
detail  drawings,  Plates  XX  to  XXIX,  getting  a  gen- 
eral idea  of  the  individual  pieces  of  the  machine.  He 
will  doubtless  turn  back  occasionally  to  the  assembly 
in  surprise  at  the  many  things  which  had  escaped  him 
in  the  maze  of  lines  making  up  the  assembly  drawing. 
He  will  also  go  back  to  the  assembly  to  locate  the 
place  of  a  part  on  the  machine  as  a  whole. 

After  a  cursory  looking  over  of  the  detail  drawings 
the  student  should  go  over  the  detail  drawings  one  by 


71 


ASSEMBLY 

FOR  8'  BENCH  GRINDER 


Plate  XIX 


72 


SR1NDER  HCAD 

FOR  6"  BtNCH  GRINDER 

SCALC  •  WO(fK    TO   DIMENSIONS 


for  ffTSlHd.  CepScrcKi  and  Waihtn.  ±  Wonted 


—   —r-  r-v   —7" 


Plate  XX 


Drill  a  dia  for 
babbitt  vent 


-Drill  6 Holes  fe'dia.  s'deep 
for  babbitt  anchors. 


2  Wan  ted.  Cast  Iron. 
Pattern  N&  2. 


HEAD  CAP 
FOR   8"  BENCH   GRINDER 

SCALE-WORK  TO  DIMENSIONS 


Plate  XXI 


74 


1  1 


Fight 


Left  Guard 

One.  Wanted      Cast  Iron       One  Wanted 
Pattern  A/"  j  Pattern  N*  4- 


SAFETY  GUARDS 


FOR  8'BENCH  GRINDER 

SCALE 'WORK    TO  DIMENSIONS 


Plate  XXII 


75 


76 


BLUE  PRINT  READING 


one  for  a  thorough  detailed  study  and  in  this  we  will 
try  to  lead  and  aid.  It  is  usually  best  to  begin  with  the 
larger  details  first  as  they  are  likely  to  influence  other 
details,  so  we  give  our  first  detailed  study  to  the 
Grinder  Head,  Plate  XX. 

We  see  the  draftsman  has  made  use  of  a  three  view 
drawing — top  view,  front  view,  and  side  view.  The 
rectangular  boundary  line  of  the  top  view  is  readily 
recognized,  after  a  confirmatory  glance  at  the  other 
two  views,  to  show  that  the  base  of  the  grinder  head  is 
rectangular  in  shape.  This  is  information  the  student 
may  have  assumed  in  the  study  of  the  assembly  but 
was  not  necessarily  so  as  without  further  information 
than  that  given  in  the  assembly  drawing  the  student 
would  have  been  just  as  much  justified  in  assuming 
that  the  base  was  elliptical,  or  oval. 

Study  of  the  front  and  side  views  show  that  the 
central  portion  of  the  grinder  head  is  somewhat  wedge 
shaped.  A  note  on  the  front  view  calls  attention  to  the 
fact  that  the  corners  are  rounded  off.  The  student  will 
find  this  same  information  given  by  a  radius  dimen- 
sion in  the  top  projection. 

The  side  view  shows  very  clearly  large  projecting 
lugs  on  the  back  and  front.  The  top  and  front  views 
show  that  there  are  four  of  these  lugs,  two  at  each  end. 
A  note  shows  that  these  lugs  are  drilled  with  y4"  holes. 


Reference  to  the  assembly  shows  that  these  holes  are 
for  the  Rest  Brackets  to  go  into. 

The  upper  part  is  clearly  a  double  bearing.  It  is 
shown  with  babbitt  bearings  in  place.  The  small  finish 
marks  (/)  show  that  the  top  and  ends  of  each  of  the 
bearings  is  to  be  finished. 

The  note  in  the  upper  right  part  of  the  plate  gives 
the  number  of  these  grinder  heads  required  for  the 
machine  and  also  of  what  material  it  is  to  be  made. 

The  next  drawing  the  student  will  direct  his  atten- 
tion to  is  the  Head  Cap — Plate  XXI.  In  most  respects 
it  is  like  the  top  of  the  Grinder  Head. 

Much  of  the  details  given  by  this  drawing  are  seen 
to  be  a  duplication  of  similar  parts  in  the  top  of  the 
Grinder  Head.  The  babbitt  bearing  part  is  seen  to  be 
exactly  a  duplicate  except  for  the  oil  hole  drilled 
through  the  top  and  a  babbitt  vent  as  an  aid  in  pouring 
the  bearing.  Screw  threads  and  a  note  show  that  an  oil 
cup  is  to  be  screwed  into  the  oil  hole.  The  holes  for 
fastening  the  Cap  onto  the  Head  are  not  threaded  as 
they  were  in  the  Grinder  Head.  A  note  states  that  each 
machine  is  to  have  two  of  these  caps  and  that  they  are 
to  be  made  of  cast  iron. 

In  the  drawing  Safety  Guards — Plate  XXII, — the 
student  will  note  a  quite  common  practice  among 
draftsmen — that  of  combining  similar  parts  so  that 


/i" 


±* 


-t- 


.L£.  u.s.sta 

for  Case-Hardened  Hen  Nut. 


•I3f 


"  Overall 


•te 


sJDrill  for  set  screw 


-/i- 


One  Wanted.  Mild  Stetl. 


-«- 


r/i" — 
4 


4 


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^»r  Case-Hardened  Hex  M^-, 
One  Wanted         / 


SPINDLE 


FOR  8'  BENCH  GRINDER 

SCALE -WORK    TO  DIMENSIOM5 


Plate  XXlll 


77 


.75  Bore  for  Press  Fit-, 


2jWantedt  Cast  Iron 
Pattern  N*-  6 


OUTSIDE  FLANGE 

FOR  8"  BENCH  GRINDER 

SCA.LE «  WORK   TO  DIMENSIONS 


Plate  XXIV 


78 


75  Bore,  for  Press  Fit: 


Inside.  Flange. 
2  Wanted.  Cast  Iron 
Pattern  A/2  S 


Finish  all  over. 


INSIDE  FLANGE 


FOR  8"  BENCH  6RIMDER 

SCALE  -   WORK   TO  DIMENSIONS 


Plate  XXV 


79 


80 


BLUE  PRINT  READING 


.one  view  serves  for  two  drawings.  This  is  a  drawing 
of  two  separate  guards,  one  for  the  left  and  one  for  the 
right  of  the  machine.  The  right  guard  is  drawn  with 
a  front  and  right  side  view  but  only  a  front  view  of  the 
left  guard  is  shown.  Evidently  the  side  view  of  the 
right  guard  is  to  be  interpreted  as  being  the  same  for 
both  guards.  The  draftsman  has  made  use  of  an 
auxiliary  view  of  the  bottom  omitting  from  the  view 
all  parts  already  sufficiently  illustrated  in  the  other 
views. 

In  the  drawing  of  the  Spindle— Plate  XXIII — the 
draftsman  has  made  use  of  a  convention  often  used  in 
machine  drawings  but  not  explained  heretofore  in  this 
book.  This  is  the  use  of  the  large  crossing  lines  in 
the  2  9/16"  lengths  of  the  spindle.  Crossing  lines  thus 
used  on  a  machine  drawing  indicate  a  bearing  surface 
and  serve  to  put  the  machinist  on  notice  to  be  careful 
of  the  size  and  finish  of  the  surfaces. 

The  student  should  note  that  there  is  a  difference 
in  the  threading  of  the  two  ends.  This  will  explain 
the  reason  for  two  drawings  of  the  hexagonal  nuts. 
The  draftsman  could  have  combined  these  similar  to 
the  drawing  of  the  guards  in  the  previous  plate  using 
these  views,  or  he  could  have  drawn  but  one  drawing 
of  two  views  drawing  the  hidden  edge  lines  represent- 
ing the  threads  horizontally  and  depending  upon  a 


note  to  explain  that  one  was  to  be  made  with  right 
hand  threads  and  one  with  left  hand  threads.  The 
draftsman  evidently  thought  that  the  saving  of  these 
few  lines  hardly  justified  the  risk  of  error  involved. 

The  student  will  note  the  use  of  decimal  fractions 
to  insure  extreme  accuracy  in  those  parts  involving 
pressed  fits. 

In  the  drawings  for  the  flanges,  Plates  XXIV  and 
XXV,  two  view  drawings  are  used.  The  student 
should  note  however  that  one  view  is  rendered  half  in 
section  as  discussed  in  the  latter  part  of  Chapter 
VIII. 

The  Spindle  Pulley,  Plate  XXVI,  is  readily  recog- 
nized as  a  solid  cast  iron  pulley,  crowned  in  the  center 
and  intended  to  be  held  in  place  by  a  headless  set 
screw. 

In  the  drawing  of  the  Rest  Brackets,  Plate  XXVII, 
the  student  will  note  that  the  draftsman  has  made  one 
drawing  serve  for  three  different  length  rest  brackets 
by  the  simple  expedient  of  dimensioning  the  length 
with  these  different  dimension  lines  and  placing  a  note 
stating  the  members  wanted  after  each  dimension.  In 
order  not  to  have  his  drawing  out  of  scale  for  two  of 
the  dimensions  he  has  resorted  to  a  break.  The  break 
also  helps  to  establish  the  fact  that  the  shaft  of  the 
bracket  rest  is  round  though  the  word  "turn"  used 


rSJJrill.  %"Tap.l6Th'd. 
for  jf V x "Hcactle ss  Set  Screw.  One  Wanted. 


tr 

»-: 

I 

:-3 

£1  

- 

*  

*•       ] 

'M 

One  Wanted.  Cast  Iron.     Ft'nish  all  over. 
Pattern  N*  7 


SPINDLE:  PULLEY 

FOR  8'  BENCH  GRINDER 

SCALE  -WORK   TO  DIMENSIONS 


Plate  XXVI 


81 


Ffest  Brackets  -Cast  Iron. 


•&Drillt  j'Tap.  IBThd- 
for  £x$£q.HjJ  Set  Sere* 

±Wanted_ 


One.  Wanted    Pat.  N*  8 
One  Wanted  Pat.  N*  g_ 

Z-Wantcd.  Pat. 


REST  BRACKETS 

FOR  8"  BENCH  GRINDER 

SCALE  •  WORK,   TO  DIMENSIONS 


Plate  XXVII 


82 


Pattern  Ns  12. 


T-RE5T 

FOR  8"  BENCH  GRINDER 

SCALE  -  WORK   TO  DIMENSIONS 


Plate  XXVIII 


83 


84 


BLUE  PRINT.  READING 


in  connection  with  the  3/4"  dimension  also  make  this 
clear. 

The  drawings  of  the  angle  rest  and  T-rest,  Plates 
XXIII  and  XXIX,  are  so  sirr.ple  as  to  involve  no 
problems  for  the  student  to  readily  interpret  them. 

It  will  be  well  for  the  student  to  refer  back  and 
forth  from  plate  to  plate  as  he  studies  these  drawings 
much  as  one  might  read  a  newspaper  by  reading  head- 
lines and  the  more  interesting  news  items  first  then 
finally  the  intervening  matter  not  at  first  given  atten- 
tion to. 

QUESTIONS   ON   THE   8"   BENCH    GRINDER. 

1.  What  holds  the  babbitt  bearings  in  place? 

2.  What    does    the    dotted    line    weaving    back    and    forth 
around  the  edges  of  the  top  view  of  Plate  XX  locate? 

3.  How  thick  are  the  side  walls  of  the  grinder  head? 

4.  How  large  a  surface  will  the  base  of  the  grinder  cover? 

5.  How  far  apart  are  the  centers  of  the  holes  for  bolting 
the  machine  to  the  bench — both  ways? 

6.  What  diameter  lag  screws  or  bolts  are  to  be  used  to 
fasten  this  machine  to  the  bench? 

7.  The  top  view  shows  a  %"  hole  at  the  exact  center.    How 
is  this  hole  to  be  made? 


8.  Is  the  bottom  of  the  grinder  head  to  be  left  rough  or  is 
it  to  be  planed  off? 

9.  Why  are  there  four  3/8"  tapped  holes  in  the  bottom  or 
flanged  part  of  the  grinder  head? 

10.  Are  bolts  or  cap  screws  to  be  used  in  fastening  the  caps 
on  to  the  top  of  the  grinder  head? 

11.  What  do  each  of  the  three  concentric  circles  at  the  back 
of  the  top  view  of  the  head  cap  indicate? 

12.  How  many  threads   per  inch  must  be   on  the   oil   cups 
which  go  in  the  head  caps? 

13.  How  many  finished  surfaces  on  the  head  cap? 

14.  What  do  you  figure  to  be  the  extreme  width  of  the  head 
caps,  from  back  to  front? 

15.  Is  the  height  given? 

16.  Are  the  holes  for  the  cap  screws  which  hold  the  cap  in 
place  on  the  grinder  head  drilled  or  cored? 

17.  Are    the   surfaces   under   these   cap   screw   heads   to    be 
machined? 

18.  How  thick  is   the  metal   at  the   point  where   these   cap 
screws  go  through? 

19.  Are  the  bottoms   of  the   guards  to  be  machined  off  or 
left  rough? 

20.  Represent  the   two   hex.   nuts   on   Plate   XXIII   by   one 
drawing  as  the  draftsman  used  in  representing  the  right 
and  left  guards,  Plate  XXII. 


•T-t 


itt* 


$ 


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% 


^1 


-is*! 


vf 


^ 


<7/?e  Wanted  Cast  Iron 
Pattern  A/3  // 


ANGLE  REST 
8"  BENCH  GRINDER 


SCALE  •  WORK    TO  DIMENSIONS 


Plate  XXIX 


85 


86 

21.     Is  the  central  V/s"  length  of  the  spindle  round  or  square 
and  how  do  you  know? 


22.     Are  square,  V,  or  U.  S.  standard  threads  to  be  used  and 
how  many  threads  per  inch? 


BLUE  PRINT  READING 

32.  How  many  rest  brackets  are  needed  for  the  grinder? 

33.  How  much  of  the  rest  brackets  are  to  be  machined  off? 

34.  Of  what  material  are  the  rest  brackets  to  be  made? 


23.  Are  the  nuts  to  receive  any  special  treatment  that  is  not 
called  for  for  the  spindle? 

24.  Are  the  stone  side  faces  of  the  flanges  to  be  machine 
finished? 

25.  Are  holes  in  the  two  flanges  to  be  of  the  same  size? 

26.  Is  the  spindle  the  same  diameter  where  it  supports  out- 
side and  inside  flanges? 

27.  How  is  the  inside  flange  to  fit  on  the  spindle? 

28.  Why  are  two  dotted  circles  on  the  face  view  of  the  inside 
flange  and  only  one  on  the  outside  flange? 

29.  Why  are  there  two  circles  used  in  representing  the  out- 
side of  the  end  of  the  spindle  pulley? 

30.  How  much  crown  is  the  pulley  to  have? 

31.  How  is  the  pulley  to  be  fastened  to  the  spindle? 


35.  How   many   steel   parts   in   this   machine   not   including 
stock  parts  not  detailed? 

36.  Make  a  bill  of  necessary  accessories  not  detailed,  such 
as   grinder   wheels,    bolts,    screws,    etc.,    giving   number 
needed,   size   and   other   information   necessary   for   or- 
dering. 

37.  What  is  the  overall  length  and  height  of  the  machine? 

38.  What  width  belt  would  be  needed  to  belt  up  the  ma- 
chine? 

39.  What  size  bolts  to  bolt  it  on  to  a  2"  bench  top?     How 
many? 

40.  What  scale  are  these  drawings  drawn  at? 

41.  Which  of  the  five  kinds  of  drawings  discussed  in  Chap- 
ter I,  has  the  draftsman  used  in  detailing  the  grinder? 


YC  66274 


M128208 


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